# At what depth on Mars would the atmosphere have equal pressure of that on Earth?

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I know the atmospheric pressure on Mars is less than that of Earth, and so is its gravity. However, I know that the deeper you go (e.g. in a cave or a hole that is dug), the more atmospheric pressure you would experience. How deep would you have to go on Mars (e.g. below the surface) for the atmospheric pressure to be equal to the pressure we experience on the surface of the earth?

Nasa has a atmospheric model of mars: $$0.699 *e^{-0.00009 h}$$

A naive application of this model, solving for a pressure of 101 kPa, gives a depth of -55 km.

The Armstrong limit depth (at which water boils at body temperature) is -24km

The model assumes constant temperature, and gravity (it doesn't correct for the fact that at 55 km below the surface you would be well into the martian mantle and the temperature would be very much higher, and deep enough for a measurable difference in gravity). There's no "goldilocks depth" at which you would only need an oxygen supply.

These depths are not achievable with current technology. The deepest mines on Earth are about 4km deep, and even the Kola superdeep borehole only managed 12km

## Mars terraforming not possible using present-day technology

This artist’s concept depicts the early Martian environment (right)—believed to contain liquid water and a thicker atmosphere—versus the cold, dry environment seen at Mars today (left). (Courtesy NASA Goddard Space Flight Center)

Science fiction writers have long featured terraforming, the process of creating an Earth-like or habitable environment on another planet, in their stories. Scientists themselves have proposed terraforming to enable the long-term colonization of Mars. A solution common to both groups is to release carbon dioxide gas trapped in the Martian surface to thicken the atmosphere and act as a blanket to warm the planet.

However, Mars does not retain enough carbon dioxide that could practically be put back into the atmosphere to warm Mars, according to a NASA-sponsored study led by LASP Associate Director for Science Bruce Jakosky. Transforming the inhospitable Martian environment into a place astronauts could explore without life support is not possible without technology well beyond today’s capabilities.

Although the current Martian atmosphere itself consists mostly of carbon dioxide, it is far too thin and cold to support liquid water, an essential ingredient for life. On Mars, the pressure of the atmosphere is less than one percent of the pressure of Earth’s atmosphere. Any liquid water on the surface would very quickly evaporate or freeze.

Proponents of terraforming Mars propose releasing gases from a variety of sources on the Red Planet to thicken the atmosphere and increase the temperature to the point where liquid water is stable on the surface. These gases are called “greenhouse gases” for their ability to trap heat and warm the climate.

“Carbon dioxide (CO2) and water vapor (H2O) are the only greenhouse gases that are likely to be present on Mars in sufficient abundance to provide any significant greenhouse warming,” said Jakosky, a CU Boulder professor of geology and lead author of the study appearing in Nature Astronomy July 30.

### Ice, dust, and rock

Although studies investigating the possibility of terraforming Mars have been made before, the new result takes advantage of about 20 years of additional spacecraft observations of Mars.

“These data have provided substantial new information on the history of easily vaporized (volatile) materials like CO2 and H2O on the planet, the abundance of volatiles locked up on and below the surface, and the loss of gas from the atmosphere to space,” said co-author Christopher Edwards of Northern Arizona University, Flagstaff, Arizona.

The researchers analyzed the abundance of carbon-bearing minerals and the occurrence of CO2 in polar ice using data from NASA’s Mars Reconnaissance Orbiter and Mars Odyssey spacecraft, and used data on the loss of the Martian atmosphere to space by the LASP-led MAVEN (Mars Atmosphere and Volatile Evolution) spacecraft.

“Our results suggest that there is not enough CO2 remaining on Mars to provide significant greenhouse warming were the gas to be put into the atmosphere in addition, most of the CO2 gas is not accessible and could not be readily mobilized. As a result, terraforming Mars is not possible using present-day technology,” said Jakosky.

The atmospheric pressure on Mars is around 0.6 percent of Earth’s. With Mars being further away from the Sun, researchers estimate a CO2 pressure similar to Earth’s total atmospheric pressure is needed to raise temperatures enough to allow for stable liquid water. The most accessible source is CO2 in the polar ice caps it could be vaporized by spreading dust on it to absorb more solar radiation or by using explosives. However, vaporizing the ice caps would only contribute enough CO2 to double the Martian pressure to 1.2 percent of Earth’s, according to the new analysis.

Another source is CO2 attached to dust particles in Martian soil, which could be heated to release the gas. The researchers estimate that heating the soil could provide up to 4 percent of the needed pressure.

A third source is carbon locked in mineral deposits. Using the recent NASA spacecraft observations of mineral deposits, the team estimates the most plausible amount will yield less than 5 percent of the required pressure, depending on how extensive deposits buried close to the surface may be. Just using the deposits near the surface would require extensive strip mining, and going after all the CO2 attached to dust particles would require strip mining the entire planet to a depth of around 100 yards. Even CO2 trapped in water-ice molecule structures, should such “clathrates” exist on Mars, would likely contribute less than 5 percent of the required pressure, according to the team.

Carbon-bearing minerals buried deep in the Martian crust might hold enough CO2 to reach the required pressure, but the extent of these deep deposits is unknown, not evidenced by orbital data, and recovering them with current technology is extremely energy intensive, requiring temperatures above 300 degrees Celsius (over 572 degrees Fahrenheit). Shallow carbon-bearing minerals are not sufficiently abundant to contribute significantly to greenhouse warming, and also require the same intense processing.

This infographic shows the various sources of carbon dioxide on Mars and their estimated contribution to Martian atmospheric pressure. (Courtesy NASA Goddard Space Flight Center)

### Atmospheric loss

Although the surface of Mars is inhospitable to known forms of life today, features that resemble dry riverbeds and mineral deposits that only form in the presence of liquid water provide evidence that, in the distant past, the Martian climate supported liquid water at the surface. But solar radiation and solar wind can remove both water vapor and CO2 from the Martian atmosphere.

Both MAVEN and the European Space Agency’s Mars Express missions indicate that the majority of Mars’ ancient, potentially habitable atmosphere has been lost to space, stripped away by solar wind and radiation. Of course, once this happens, that water and CO2 are gone forever. Even if this loss were prevented somehow, allowing the atmosphere to build up slowly from outgassing by geologic activity, current outgassing is extremely low it would take about 10 million years just to double Mars’ current atmosphere, according to the team.

This research was supported in part by NASA through the MAVEN and Mars Odyssey THEMIS (Thermal Emission Imaging System) projects.

## Should We Terraform Mars? Let’s Recap

I t seemed inevitable that Elon Musk would eventually get into a Twitter war over whether Mars can be terraformed. When you’re on Twitter, he told Businessweek in July, 2018, you’re “in meme war land.” “And so essentially if you attack me,” he said, “it is therefore okay for me to attack back.”

Musk, the CEO and lead designer of SpaceX, wants to “make life multiplanetary,” starting with Mars. “Public support for life on Mars is critical to making it happen,” he tweeted last week. The red planet is relatively close to the Earth and once harbored surface seas and rivers, and it still has ice and a subsurface lake. Its weather is surprisingly workable, too. Mars’ surface temperature range (–285 to 88 degrees Fahrenheit) isn’t too far off from Earth’s (–126 to 138 degrees Fahrenheit). The problem is Mars’ atmosphere now has 0.006 bar of pressure, where one bar is the standard atmospheric pressure at sea level on Earth. Not only does this mean that dangerous levels of radiation reach the surface unchecked, but humans need at least 0.063 bar to keep our bodily liquids from boiling (this is called the Armstrong limit).

Enter terraforming—changing a planet’s climate, topography, or ecology to be more suitable for life. If we could boost the pressure of Mars’ atmosphere just above that of Mount Everest’s summit (0.337 bar), we could walk on the Martian surface using just a breathing mask—no pressurized space suit required. That might be called weak terraforming: It wouldn’t let plants grow in the soil outside of greenhouses.

home sweet mars: An artist’s rendition illustrating what the early Martian environment could have once been like, compared with how it is today. NASA’s Goddard Space Flight Center

For that, a good amount of nitrogen, more than scientists have spotted so far on Mars’ surface, is required. It also wouldn’t let us breathe the Martian air. But Musk thinks that, at the least, weak terraforming is possible: “In fact,” he told an audience at the International Astronautical Congress in Mexico in 2016, “if we could warm Mars up, we would once again have a thick atmosphere and liquid oceans.”

No—not any time soon. At least, that’s according to the latest look at the idea from NASA’s principal investigator for the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft, Bruce Jakosky, a space scientist at the University of Colorado, Boulder. He says the growing popularity of terraforming—driven in part by Musk—persuaded him and Christopher Edwards, a geologist also at Boulder, to gauge whether it was feasible. Their answer: No, it “is not possible using present-day technology.” In their July 2018 Nature Astronomy paper, they mention Musk directly, shooting down his idea of terraforming by nuking Mars’ polar ice caps. The amount of frozen CO2 released would not be enough to induce a runaway greenhouse effect, they argue. Shortly afterward, Discover magazine singled out Musk in a tweet linking to the headline: “Sorry, Elon. There’s Not Enough CO2 to Terraform Mars.”

So Musk counter-attacked. “There’s a massive amount of CO2 on Mars adsorbed into soil that’d be released upon heating,” he tweeted at Discover. “With enough energy via artificial or natural (sun) fusion, you can terraform almost any large, rocky body.” The next day on Twitter, Musk replied twice to a Discover tweet rebutting his comment. First, he tweeted, in part: “Oh yeah? I’ll see ur expert & raise you a Chris McKay @NASA.” Then, three minutes later: “Science” followed by an emoji heart, microscope, shooting star, and a link to a 1993 paper McKay co-authored, titled “Technological Requirements for Terraforming Mars.”

If Mars has lost 75 percent of its atmospheric CO2 to space, then barely any of it has been stored in the ground near enough to the surface for humans to be able to mobilize it.

Why would Musk put his trust in McKay, a NASA Ames Research Center planetary scientist, over other experts? I asked McKay if he’d seen Jakosky and Edwards’ Nature Astronomy paper. The paper notes that MAVEN, since 2014, and the Mars Express spacecraft, since 2003, have observed Mars lose part of its atmosphere to space in real time, and that the Mars Reconnaissance Orbiter and the Mars Odyssey spacecraft have analyzed the “abundance of carbon-bearing minerals and the occurrence of CO2 in polar ice.” These new data points, they say, indicate that, first, the majority of Mars’ ancient, thick atmosphere has been lost to space, not transferred back into still-undetected shallow reservoirs of CO2 beneath the surface and second, that whatever amount of CO2 is left in the ground, it is “not accessible and thus cannot be readily mobilized” into the atmosphere.

“I know this paper,” McKay said, “They are correct that, indeed, the key question for terraforming is the amount of CO2, N2, and H2O on Mars. Unfortunately there is nothing new here to resolve this question.” In McKay’s opinion, the new data that Jakosky and Edwards point to just isn’t good enough.

McKay drew my attention to a 1991 paper he wrote in Nature with two colleagues, Owen Toon and James Kasting, titled, “Making Mars habitable.” What he concluded then—about how the amount and distribution of carbon dioxide, water, and nitrogen on Mars is unclear—is still true today, he told me. “We are still highly uncertain as to the amount of CO2 below the surface. We don’t have good data and will need to drill deeply to get it.” He said Jakosky and Edwards’ conclusion that near-term terraforming is impossible is “premature.”

He isn’t alone in this view. McKay is joined by Robert Zubrin, his co-author on the 1993 terraforming paper. Zubrin is an aerospace engineer, author, and founding president of the Mars Society, a non-profit which advocates terraforming Mars. Building a civilization there would “add to the strength and vitality of human culture” on Earth, Zubrin told NBC News. He has also argued that Mars should be the goal of NASA’s space program.

#### Ingenious: Caleb Scharf

What inspired a boy who grew up in the English countryside to study astronomy? Looking up at the starry night sky, of course. But you have to hear Caleb Scharf tell the story himself – tell how his boyhood curiosity. READ MORE

Ask Zubrin what he makes of Jakosky: He is “not only pretending to knowledge he doesn’t have, but which is in flat contradiction to the known data.” For example, the results Jakosky highlighted in his Nature Astronomy paper indicate that at least 75 percent of ancient Mars’ atmospheric CO2—0.5 bar of it—floated away billions of years ago, possibly driven out by solar wind and extreme ultraviolet light, among other things. If Mars has lost at least 75 percent of its atmospheric CO2 to space, then that means barely any of that early thick atmosphere—amounting to less than a bar, according to Jakosky—has been stored in the ground near enough to the surface for humans to be able to mobilize it. “Obviously,” Jakosky and Edwards write, “once gas has been lost to space, it is no longer available to be mobilized back into the atmosphere.” To them that leaves only a paltry amount of accessible CO2 left in the ground: 0.020 bar.

Jakosky calculates that 75 percent loss in the following way: Assume the solar-wind and UV-light activity observed today also operated in the past but with greater intensity (something he believes to be true, based on a history of the sun derived from sun-like stars). Then, take the ratio today of carbon 13 to 12 in the Martian atmosphere, and compare it to the ratio of carbon 13 to 12 in the ground. Since the heavier isotopes in the atmosphere tend to stick around, while the lighter ones fly away, the degree to which atmospheric CO2 is enriched with the heavier isotope will differ relative to ground-based carbon. That difference indicates, Jakosky and Edwards write, that at least three-quarters of Mars’ atmospheric CO2 is gone and that “loss to space was the dominant process for removing the ancient CO2 greenhouse atmosphere.” This is opposed to the idea, backed by Zubrin and McKay, that another process could have removed CO2 from the atmosphere but kept it on the planet—either adsorption into the soil, freezing as CO2 ice, or getting locked up in carbon-bearing minerals.

searching for data: The curiosity Mars rover. NASA

This is where, to Zubrin and McKay, Jakosky seems to contradict the known data. 0.5 bar of atmospheric CO2 loss is a fair—even if not conclusive—assessment, McKay and Zubrin told me. (McKay: “There is some debate if they are actually measuring CO2 loss or just O2 loss.” Zubrin: “That claim is controversial, but we’ll let it pass because at least in that case [Jakosky] is arguing from data.”) What they disagree with is Jakosky’s carbon isotope analysis. Zubrin said it is impossible for the 0.5 bar of atmospheric CO2 loss to represent 75 percent or more of Mars’ original atmospheric total because, “based on the available data on liquid water on ancient Mars, Mars must have had at least 2 bar of CO2” enveloping the planet (the ground-based amount at that time is unknown). If so, contrary to Jakosky, there would be well over a bar left in shallow ground deposits somewhere—enough to trigger a runaway greenhouse effect if vaporized.

Plus, Zubrin pointed out, scientists don’t know what the original carbon 12 to 13 ratio of the planet was, which Jakosky more or less concedes in his paper. (He extrapolates the ratio on ancient Mars from Martian meteorites.) Most importantly, Jakosky “doesn’t know what the C12/C13 ratio in the subsurface soil is,” Zubrin added. “It could be very different from the atmospheric ratio, because if most of the CO2 was immobilized in the regolith”—the layer of unconsolidated rocky material covering bedrock—“billions of years ago, while most of the atmosphere was lost to space, the two reservoirs would be left with entirely different contents.” McKay echoed this. “The isotope data only refers to the carbon reservoirs that exchange with the atmosphere,” he said. “Carbonate rocks and CO2 ice deposits that are isolated from the atmosphere will not be indicated by the carbon isotope ratio at the surface.”

The ice cap at the South Pole, for example, is one region harboring isolated deposits. “These are not well understood nor is their extent fully determined,” McKay said. He pointed out a 2016 study, in which scientists mapped what they could of the region remotely, using the Shallow Radar instrument on Mars Reconnaissance Orbiter, and found that there’s enough subsurface CO2 ice to double Mars’s atmospheric pressure, to 0.012 bar, if it were vaporized.

Of course, that’s nowhere near a sufficient amount to allow humans to walk on Mars without a pressurized suit. Many more deposits of CO2 capable of being released into the atmosphere must be found. The deposits at the South Pole “are relatively young,” McKay said. “But old, deeper deposits may exist.” For him, the results from the MAVEN and Mars Express spacecrafts are “a plus” because “virtually all climate models suggest that early Mars must have had several bars of CO2 early in its history,” he said. “So there must be bars still left there” in shallow ground deposits, buried for billions of years.

Imagine someone on Mars, in 1890, estimating Earth’s oil reserves without ever having drilled there.

I put this to Jakosky. He replied he believes there’s almost no CO2 (about the equivalent of 0.020 bar) left on or near the surface that can be vaporized. This estimate is based both on his atmospheric CO2-loss analysis and on the fact that large amounts of CO2 haven’t been hinted at on the surface, which humans have probed to a depth of 10 centimeters. It also hasn’t been exposed in a half-dozen other locations—impact craters and massive trenches, like Valles Marineris, the Grand Canyon of Mars. These two types of surface features show layers of the crust at various depths.

So any buried CO2 must be deeper still, in hard-to-reach places. “You have to make assumptions about what you can’t see,” Jakosky told me. There might be a lot of buried, “deep carbonate” CO2 still left on Mars, but it can’t be reached. “While there is no formal upper limit on the amount of carbonate deposits—one could always argue that they are preferentially sequestered in locations that we have not or cannot observe—such deposits are both geologically implausible and difficult or impossible to access for terraforming,” he and Edwards write.

McKay’s takeaway from the same information is less pessimistic and less conclusive. “Unfortunately we have not learned much about the subsurface of Mars over the past 20 years. More data please,” he told me. “This planet is the size of Earth’s continents and appears very different in different locations.” Zubrin invited me to imagine someone on Mars, in 1890, estimating Earth’s oil reserves without ever having drilled there: “That’s the position Jakosky is in,” he said. “It’s ridiculous, absurd.”

If Jakosky is wrong, and Mars really does have multiple bar-equivalent of buried CO2 that we can access, we could potentially terraform Mars rapidly. “To judge from how quickly our greenhouse emissions are warming Earth, we could shift Mars into a warm climate state within 100 years,” McKay explained in his Nautilus feature. “The most efficient technique would be to produce supergreenhouse gases such as chlorofluorocarbons or, better, perfluorinated compounds, which are not toxic, do not interfere with the development of an ozone layer, and resist destruction by solar ultraviolet radiation. Curiosity has confirmed the presence of fluorine in the rocks on Mars, so the ingredients are all there.”

In a 2001 paper, McKay and aeronautical engineer Margarita Marinova, now the Senior Mars and Vehicle Systems Development Engineer at SpaceX, wrote, “On the order of 4x10 20 Jules, equivalent to about 75 minutes of Martian sunlight, will be required to produce enough [perfluorocarbons] to raise the temperature of Mars” by about 9 degrees Fahrenheit. “This is equivalent to 250 facilities consuming 500 MW (the size of a small nuclear reactor) working for 100 years.” Lots of people will be needed to staff those facilities, in addition to those providing for the colony’s other needs, like agriculture. Zubrin believes that half a million to a million people will be needed to start substantial terraforming.

Whether we can terraform Mars or not, it does look like we’ll be visiting soon. Musk has a plan to get us there using SpaceX’s Starship. A few of them, after landing, will form “Mars Base Alpha.” In Australia, he showed it to an audience along with pictures depicting the growth of the base into a town and then a city. Eventually, Mars’ new inhabitants will terraform Mars, he said. It will be “a nice place to be.”

Brian Gallagher is an associate editor at Nautilus. Follow him on Twitter @bsgallagher.

This article first appeared in our “In Plain Sight” issue in October 2018.

## Why Mars lost its atmosphere?

For knowing the answer to this question, we have to go back around 4.1 billion years ago. When the core of the Red planet ceased to move slowly by tightening, and Mars started losing its magnetic field. Even as, the red planet lost its magnetic field, then it lost its protective armor which was protecting it from the harmful solar wind.

Now the energy particles which were coming from the Sun were colliding with molecules of the red planet and converting them to ions.

When these ions went in the circle of the magnetic field of our sun, then these ions started moving in the direction of the magnetic field with spiral speed. So in this way, these ions escaped the gravity and left the Martian atmosphere.

This is the reason that the Martian atmosphere was destroyed and became thin. The layers of gases in the Martian atmosphere became very thin. Moreover, the atmospheric pressure of Mars was almost over, and the temperature became very low.

So due to the run out of the atmospheric pressure, the pressure required to retain the liquid water on the red planet could not even be found. That’s why water does not last on the surface of Mars.

## Can a Mars Colony be built so deep underground that it's pressure and temp is equal to Earth?

Just seems like a better choice if its possible. No reason it seems to be exposed to the surface at all unless they have to. Could the air pressure and temp be better controlled underground with a solid barrier of rock and permafrost above the colony? With some artificial lighting and some plumbing, couldn't plant biomes be easily established there too? Sorta like the Genesis Cave

Short answer: If you wanted to dig on Mars to reach a depth where the pressure would be 1 atmosphere, i.e. equivalent to sea level pressure on Earth, it would most likely be much too warm.

Long answer: Consider the case of Death Valley on Earth. Since it lies below sea level, the atmospheric pressure there is actually greater than what's found at sea level, roughly 1.1 1.01 atmospheres. Similarly, we could dig below the surface of Mars so that the weight of the overlying atmosphere would be the equivalent of 1 atmosphere.

We can calculate how deep a hole one must dig by using the "scale height" - this is the difference in altitude needed to produce a factor of e = 2.718x increase in pressure. In Mars' case, this is equal to 11.1 km.

Now, the pressure at the surface of Mars is a measly 0.006 atmospheres, while we want to go to 1 atmosphere. The number of scale heights we want to dig is then:

ln (1.0 / .006) = 5.12 scale heights

. which, for a 11.1 km scale height means we want to dig 5.12 * 11.1km = 56.8 km. Note that this is over 4 times deeper than the deepest hole ever dug on Earth, so this is already a pretty tough technological achievement.

Now, how warm would it be when we get there? For this, we need to consider the adiabatic lapse rate this tells us how much the temperature drops as we ascend in the atmosphere, or similarly how much the temperature increases as we descend. (It's also for this reason that Death Valley has the highest temperatures recorded on Earth.)

In the case of Mars, the adiabatic lapse rate is 4.4K/km. In other words, for every kilometer we descend, the temperature increases by 4.4 K.

Thus by descending 56.8 km, we're increasing the temperature by 56.8 * 4.4 = 250K. Since Mars' average temperature is 223 K (= -50 C, -58 F), that means the final temperature at 1 atmosphere of pressure would be 473K (= 200 C, 391 F).

EDIT: Since a lot of people are asking:

This is unrelated to whether Mars has a "dead core" or not. This temperature increase is not due to geothermal (or in this case, areothermal) energy. Rather, it's a simple consequence of taking the current atmosphere and compressing it adiabatically as it fills up our hole. A similar transformation would be suddenly opening the doors on a pressurized jet at 33,000 feet. the air would quickly expand to the thin ambient pressure and cool down in the process by 65 o - 98 o C, depending on how humid the air inside the airplane was.

You can't generate electricity from this temperature change. It seems counter-intuitive, but even though the temperature has increased, there's no extra energy added to the system - this is the definition of an adiabatic transformation.

## New Research Explains Loss of Carbon in Martian Atmosphere

This graphic depicts paths by which carbon has been exchanged among Martian interior, surface rocks, polar caps, waters and atmosphere, and also depicts a mechanism by which it is lost from the atmosphere with a strong effect on isotope ratio. Credits: Lance Hayashida/Caltech

New research from Caltech and NASA offers an explanation for the “missing” carbon in the Martian atmosphere, showing that a transition from a moderately dense atmosphere to the current thin one is entirely possible.

Mars is blanketed by a thin, mostly carbon dioxide atmosphere — one that is far too thin to keep water from freezing or quickly evaporating. However, geological evidence has led scientists to conclude that ancient Mars was once a warmer, wetter place than it is today. To produce a more temperate climate, several researchers have suggested that the planet was once shrouded in a much thicker carbon dioxide atmosphere. For decades that left the question, “Where did all the carbon go?”

The solar wind stripped away much of Mars’ ancient atmosphere and is still removing tons of it every day. But scientists have been puzzled by why they haven’t found more carbon — in the form of carbonate — captured into Martian rocks. They have also sought to explain the ratio of heavier and lighter carbons in the modern Martian atmosphere.

Now a team of scientists from the California Institute of Technology and NASA’s Jet Propulsion Laboratory, both in Pasadena, offer an explanation of the “missing” carbon, in a paper published today by the journal Nature Communications.

They suggest that 3.8 billion years ago, Mars might have had a moderately dense atmosphere. Such an atmosphere — with a surface pressure equal to or less than that found on Earth — could have evolved into the current thin one, not only minus the “missing” carbon problem, but also in a way consistent with the observed ratio of carbon-13 to carbon-12, which differ only by how many neutrons are in each nucleus.

“Our paper shows that transitioning from a moderately dense atmosphere to the current thin one is entirely possible,” says Caltech postdoctoral fellow Renyu Hu, the lead author. “It is exciting that what we know about the Martian atmosphere can now be pieced together into a consistent picture of its evolution — and this does not require a massive undetected carbon reservoir.”

When considering how the early Martian atmosphere might have transitioned to its current state, there are two possible mechanisms for the removal of the excess carbon dioxide. Either the carbon dioxide was incorporated into minerals in rocks called carbonates or it was lost to space.

An August 2015 study used data from several Mars-orbiting spacecraft to inventory carbonates, showing there are nowhere near enough in the upper half mile (one kilometer) or the crust to contain the missing carbon from a thick early atmosphere during a time when networks of ancient river channels were active, about 3.8 billion years ago.

The escaped-to-space scenario has also been problematic. Because various processes can change the relative amounts of carbon-13 to carbon-12 isotopes in the atmosphere, “we can use these measurements of the ratio at different points in time as a fingerprint to infer exactly what happened to the Martian atmosphere in the past,” says Hu. The first constraint is set by measurements of the ratio in meteorites that contain gases released volcanically from deep inside Mars, providing insight into the starting isotopic ratio of the original Martian atmosphere. The modern ratio comes from measurements by the SAM (Sample Analysis at Mars) instrument on NASA’s Curiosity rover.

One way carbon dioxide escapes to space from Mars’ atmosphere is called sputtering, which involves interactions between the solar wind and the upper atmosphere. NASA’s MAVEN (Mars Atmosphere and Volatile Evolution) mission has yielded recent results indicating that about a quarter pound (about 100 grams) of particles every second are stripped from today’s Martian atmosphere via this process, likely the main driver of atmospheric loss. Sputtering slightly favors loss of carbon-12, compared to carbon-13, but this effect is small. The Curiosity measurement shows that today’s Martian atmosphere is far more enriched in carbon-13 — in proportion to carbon-12 — than it should be as a result of sputtering alone, so a different process must also be at work.

Hu and his co-authors identify a mechanism that could have significantly contributed to the carbon-13 enrichment. The process begins with ultraviolet (UV) light from the sun striking a molecule of carbon dioxide in the upper atmosphere, splitting it into carbon monoxide and oxygen. Then, UV light hits the carbon monoxide and splits it into carbon and oxygen. Some carbon atoms produced this way have enough energy to escape from the atmosphere, and the new study shows that carbon-12 is far more likely to escape than carbon-13.

Modeling the long-term effects of this “ultraviolet photodissociation” mechanism, the researchers found that a small amount of escape by this process leaves a large fingerprint in the carbon isotopic ratio. That, in turn, allowed them to calculate that the atmosphere 3.8 billion years ago might have had a surface pressure a bit less thick than Earth’s atmosphere today.

“This solves a long-standing paradox,” said Bethany Ehlmann of Caltech and JPL, a co-author of both today’s publication and the August one about carbonates. “The supposed very thick atmosphere seemed to imply that you needed this big surface carbon reservoir, but the efficiency of the UV photodissociation process means that there actually is no paradox. You can use normal loss processes as we understand them, with detected amounts of carbonate, and find an evolutionary scenario for Mars that makes sense.”

Publication: Renyu Hu, et al., “Tracing the fate of carbon and the atmospheric evolution of Mars,” Nature Communications 6, Article number: 10003 doi:10.1038/ncomms10003

## Contents

The concept of the ablative heat shield was described as early as 1920 by Robert Goddard: "In the case of meteors, which enter the atmosphere with speeds as high as 30 miles (48 km) per second, the interior of the meteors remains cold, and the erosion is due, to a large extent, to chipping or cracking of the suddenly heated surface. For this reason, if the outer surface of the apparatus were to consist of layers of a very infusible hard substance with layers of a poor heat conductor between, the surface would not be eroded to any considerable extent, especially as the velocity of the apparatus would not be nearly so great as that of the average meteor." [3]

Practical development of reentry systems began as the range, and reentry velocity of ballistic missiles increased. For early short-range missiles, like the V-2, stabilization and aerodynamic stress were important issues (many V-2s broke apart during reentry), but heating was not a serious problem. Medium-range missiles like the Soviet R-5, with a 1,200-kilometer (650-nautical-mile) range, required ceramic composite heat shielding on separable reentry vehicles (it was no longer possible for the entire rocket structure to survive reentry). The first ICBMs, with ranges of 8,000 to 12,000 km (4,300 to 6,500 nmi), were only possible with the development of modern ablative heat shields and blunt-shaped vehicles.

In the United States, this technology was pioneered by H. Julian Allen and A. J. Eggers Jr. of the National Advisory Committee for Aeronautics (NACA) at Ames Research Center. [4] In 1951, they made the counterintuitive discovery that a blunt shape (high drag) made the most effective heat shield. [5] From simple engineering principles, Allen and Eggers showed that the heat load experienced by an entry vehicle was inversely proportional to the drag coefficient i.e., the greater the drag, the less the heat load. If the reentry vehicle is made blunt, air cannot "get out of the way" quickly enough, and acts as an air cushion to push the shock wave and heated shock layer forward (away from the vehicle). Since most of the hot gases are no longer in direct contact with the vehicle, the heat energy would stay in the shocked gas and simply move around the vehicle to later dissipate into the atmosphere.

The Allen and Eggers discovery, though initially treated as a military secret, was eventually published in 1958. [6]

Over the decades since the 1950s, a rich technical jargon has grown around the engineering of vehicles designed to enter planetary atmospheres. It is recommended that the reader review the jargon glossary before continuing with this article on atmospheric reentry.

When atmospheric entry is part of a spacecraft landing or recovery, particularly on a planetary body other than Earth, entry is part of a phase referred to as entry, descent, and landing, or EDL. [7] When the atmospheric entry returns to the same body that the vehicle had launched from, the event is referred to as reentry (almost always referring to Earth entry).

The fundamental design objective in atmospheric entry of a spacecraft is to dissipate the energy of a spacecraft that is traveling at hypersonic speed as it enters an atmosphere such that equipment, cargo, and any passengers are slowed and land near a specific destination on the surface at zero velocity while keeping stresses on the spacecraft and any passengers within acceptable limits. [8] This may be accomplished by propulsive or aerodynamic (vehicle characteristics or parachute) means, or by some combination.

There are several basic shapes used in designing entry vehicles:

### Sphere or spherical section Edit

The simplest axisymmetric shape is the sphere or spherical section. [9] This can either be a complete sphere or a spherical section forebody with a converging conical afterbody. The aerodynamics of a sphere or spherical section are easy to model analytically using Newtonian impact theory. Likewise, the spherical section's heat flux can be accurately modeled with the Fay–Riddell equation. [10] The static stability of a spherical section is assured if the vehicle's center of mass is upstream from the center of curvature (dynamic stability is more problematic). Pure spheres have no lift. However, by flying at an angle of attack, a spherical section has modest aerodynamic lift thus providing some cross-range capability and widening its entry corridor. In the late 1950s and early 1960s, high-speed computers were not yet available and computational fluid dynamics was still embryonic. Because the spherical section was amenable to closed-form analysis, that geometry became the default for conservative design. Consequently, manned capsules of that era were based upon the spherical section.

Pure spherical entry vehicles were used in the early Soviet Vostok and Voskhod capsules and in Soviet Mars and Venera descent vehicles. The Apollo command module used a spherical section forebody heat shield with a converging conical afterbody. It flew a lifting entry with a hypersonic trim angle of attack of −27° (0° is blunt-end first) to yield an average L/D (lift-to-drag ratio) of 0.368. [11] The resultant lift achieved a measure of cross-range control by offsetting the vehicle's center of mass from its axis of symmetry, allowing the lift force to be directed left or right by rolling the capsule on its longitudinal axis. Other examples of the spherical section geometry in manned capsules are Soyuz/Zond, Gemini, and Mercury. Even these small amounts of lift allow trajectories that have very significant effects on peak g-force, reducing it from 8–9 g for a purely ballistic (slowed only by drag) trajectory to 4–5 g, as well as greatly reducing the peak reentry heat. [12]

### Sphere-cone Edit

The sphere-cone is a spherical section with a frustum or blunted cone attached. The sphere-cone's dynamic stability is typically better than that of a spherical section. The vehicle enters sphere-first. With a sufficiently small half-angle and properly placed center of mass, a sphere-cone can provide aerodynamic stability from Keplerian entry to surface impact. (The half-angle is the angle between the cone's axis of rotational symmetry and its outer surface, and thus half the angle made by the cone's surface edges.)

The original American sphere-cone aeroshell was the Mk-2 RV (reentry vehicle), which was developed in 1955 by the General Electric Corp. The Mk-2's design was derived from blunt-body theory and used a radiatively cooled thermal protection system (TPS) based upon a metallic heat shield (the different TPS types are later described in this article). The Mk-2 had significant defects as a weapon delivery system, i.e., it loitered too long in the upper atmosphere due to its lower ballistic coefficient and also trailed a stream of vaporized metal making it very visible to radar. These defects made the Mk-2 overly susceptible to anti-ballistic missile (ABM) systems. Consequently, an alternative sphere-cone RV to the Mk-2 was developed by General Electric. [ citation needed ]

This new RV was the Mk-6 which used a non-metallic ablative TPS, a nylon phenolic. This new TPS was so effective as a reentry heat shield that significantly reduced bluntness was possible. [ citation needed ] However, the Mk-6 was a huge RV with an entry mass of 3,360 kg, a length of 3.1 m and a half-angle of 12.5°. Subsequent advances in nuclear weapon and ablative TPS design allowed RVs to become significantly smaller with a further reduced bluntness ratio compared to the Mk-6. Since the 1960s, the sphere-cone has become the preferred geometry for modern ICBM RVs with typical half-angles being between 10° to 11°. [ citation needed ]

Reconnaissance satellite RVs (recovery vehicles) also used a sphere-cone shape and were the first American example of a non-munition entry vehicle (Discoverer-I, launched on 28 February 1959). The sphere-cone was later used for space exploration missions to other celestial bodies or for return from open space e.g., Stardust probe. Unlike with military RVs, the advantage of the blunt body's lower TPS mass remained with space exploration entry vehicles like the Galileo Probe with a half-angle of 45° or the Viking aeroshell with a half-angle of 70°. Space exploration sphere-cone entry vehicles have landed on the surface or entered the atmospheres of Mars, Venus, Jupiter, and Titan.

### Biconic Edit

The biconic is a sphere-cone with an additional frustum attached. The biconic offers a significantly improved L/D ratio. A biconic designed for Mars aerocapture typically has an L/D of approximately 1.0 compared to an L/D of 0.368 for the Apollo-CM. The higher L/D makes a biconic shape better suited for transporting people to Mars due to the lower peak deceleration. Arguably, the most significant biconic ever flown was the Advanced Maneuverable Reentry Vehicle (AMaRV). Four AMaRVs were made by the McDonnell Douglas Corp. and represented a significant leap in RV sophistication. Three AMaRVs were launched by Minuteman-1 ICBMs on 20 December 1979, 8 October 1980 and 4 October 1981. AMaRV had an entry mass of approximately 470 kg, a nose radius of 2.34 cm, a forward-frustum half-angle of 10.4°, an inter-frustum radius of 14.6 cm, aft-frustum half-angle of 6°, and an axial length of 2.079 meters. No accurate diagram or picture of AMaRV has ever appeared in the open literature. However, a schematic sketch of an AMaRV-like vehicle along with trajectory plots showing hairpin turns has been published. [13]

AMaRV's attitude was controlled through a split body flap (also called a split-windward flap) along with two yaw flaps mounted on the vehicle's sides. Hydraulic actuation was used for controlling the flaps. AMaRV was guided by a fully autonomous navigation system designed for evading anti-ballistic missile (ABM) interception. The McDonnell Douglas DC-X (also a biconic) was essentially a scaled-up version of AMaRV. AMaRV and the DC-X also served as the basis for an unsuccessful proposal for what eventually became the Lockheed Martin X-33.

### Non-axisymmetric shapes Edit

Non-axisymmetric shapes have been used for manned entry vehicles. One example is the winged orbit vehicle that uses a delta wing for maneuvering during descent much like a conventional glider. This approach has been used by the American Space Shuttle and the Soviet Buran. The lifting body is another entry vehicle geometry and was used with the X-23 PRIME (Precision Recovery Including Maneuvering Entry) vehicle. [ citation needed ]

Objects entering an atmosphere from space at high velocities relative to the atmosphere will cause very high levels of heating. Reentry heating comes principally from two sources: [14]

, of two types:
• hot gas flow past the surface of the body and chemical recombination reactions between the object surface and the atmospheric gases

As velocity increases, both convective and radiative heating increase. At very high speeds, radiative heating will come to quickly dominate the convective heat fluxes, as convective heating is proportional to the velocity cubed, while radiative heating is proportional to the eighth power of velocity. Radiative heating—which is highly wavelength dependent—thus predominates very early in atmospheric entry while convection predominates in the later phases. [14]

### Shock layer gas physics Edit

At typical reentry temperatures, the air in the shock layer is both ionized and dissociated. [ citation needed ] [15] This chemical dissociation necessitates various physical models to describe the shock layer's thermal and chemical properties. There are four basic physical models of a gas that are important to aeronautical engineers who design heat shields:

#### Perfect gas model Edit

Almost all aeronautical engineers are taught the perfect (ideal) gas model during their undergraduate education. Most of the important perfect gas equations along with their corresponding tables and graphs are shown in NACA Report 1135. [16] Excerpts from NACA Report 1135 often appear in the appendices of thermodynamics textbooks and are familiar to most aeronautical engineers who design supersonic aircraft.

The perfect gas theory is elegant and extremely useful for designing aircraft but assumes that the gas is chemically inert. From the standpoint of aircraft design, air can be assumed to be inert for temperatures less than 550 K at one atmosphere pressure. The perfect gas theory begins to break down at 550 K and is not usable at temperatures greater than 2,000 K. For temperatures greater than 2,000 K, a heat shield designer must use a real gas model.

#### Real (equilibrium) gas model Edit

An entry vehicle's pitching moment can be significantly influenced by real-gas effects. Both the Apollo command module and the Space Shuttle were designed using incorrect pitching moments determined through inaccurate real-gas modelling. The Apollo-CM's trim-angle angle of attack was higher than originally estimated, resulting in a narrower lunar return entry corridor. The actual aerodynamic center of the Columbia was upstream from the calculated value due to real-gas effects. On Columbia ' s maiden flight (STS-1), astronauts John W. Young and Robert Crippen had some anxious moments during reentry when there was concern about losing control of the vehicle. [17]

An equilibrium real-gas model assumes that a gas is chemically reactive, but also assumes all chemical reactions have had time to complete and all components of the gas have the same temperature (this is called thermodynamic equilibrium). When air is processed by a shock wave, it is superheated by compression and chemically dissociates through many different reactions. Direct friction upon the reentry object is not the main cause of shock-layer heating. It is caused mainly from isentropic heating of the air molecules within the compression wave. Friction based entropy increases of the molecules within the wave also account for some heating. [ original research? ] The distance from the shock wave to the stagnation point on the entry vehicle's leading edge is called shock wave stand off. An approximate rule of thumb for shock wave standoff distance is 0.14 times the nose radius. One can estimate the time of travel for a gas molecule from the shock wave to the stagnation point by assuming a free stream velocity of 7.8 km/s and a nose radius of 1 meter, i.e., time of travel is about 18 microseconds. This is roughly the time required for shock-wave-initiated chemical dissociation to approach chemical equilibrium in a shock layer for a 7.8 km/s entry into air during peak heat flux. Consequently, as air approaches the entry vehicle's stagnation point, the air effectively reaches chemical equilibrium thus enabling an equilibrium model to be usable. For this case, most of the shock layer between the shock wave and leading edge of an entry vehicle is chemically reacting and not in a state of equilibrium. The Fay–Riddell equation, [10] which is of extreme importance towards modeling heat flux, owes its validity to the stagnation point being in chemical equilibrium. The time required for the shock layer gas to reach equilibrium is strongly dependent upon the shock layer's pressure. For example, in the case of the Galileo probe's entry into Jupiter's atmosphere, the shock layer was mostly in equilibrium during peak heat flux due to the very high pressures experienced (this is counterintuitive given the free stream velocity was 39 km/s during peak heat flux).

Determining the thermodynamic state of the stagnation point is more difficult under an equilibrium gas model than a perfect gas model. Under a perfect gas model, the ratio of specific heats (also called isentropic exponent, adiabatic index, gamma, or kappa) is assumed to be constant along with the gas constant. For a real gas, the ratio of specific heats can wildly oscillate as a function of temperature. Under a perfect gas model there is an elegant set of equations for determining thermodynamic state along a constant entropy stream line called the isentropic chain. For a real gas, the isentropic chain is unusable and a Mollier diagram would be used instead for manual calculation. However, graphical solution with a Mollier diagram is now considered obsolete with modern heat shield designers using computer programs based upon a digital lookup table (another form of Mollier diagram) or a chemistry based thermodynamics program. The chemical composition of a gas in equilibrium with fixed pressure and temperature can be determined through the Gibbs free energy method. Gibbs free energy is simply the total enthalpy of the gas minus its total entropy times temperature. A chemical equilibrium program normally does not require chemical formulas or reaction-rate equations. The program works by preserving the original elemental abundances specified for the gas and varying the different molecular combinations of the elements through numerical iteration until the lowest possible Gibbs free energy is calculated (a Newton–Raphson method is the usual numerical scheme). The data base for a Gibbs free energy program comes from spectroscopic data used in defining partition functions. Among the best equilibrium codes in existence is the program Chemical Equilibrium with Applications (CEA) which was written by Bonnie J. McBride and Sanford Gordon at NASA Lewis (now renamed "NASA Glenn Research Center"). Other names for CEA are the "Gordon and McBride Code" and the "Lewis Code". CEA is quite accurate up to 10,000 K for planetary atmospheric gases, but unusable beyond 20,000 K (double ionization is not modelled). CEA can be downloaded from the Internet along with full documentation and will compile on Linux under the G77 Fortran compiler.

#### Real (non-equilibrium) gas model Edit

A non-equilibrium real gas model is the most accurate model of a shock layer's gas physics, but is more difficult to solve than an equilibrium model. The simplest non-equilibrium model is the Lighthill-Freeman model developed in 1958. [18] [19] The Lighthill-Freeman model initially assumes a gas made up of a single diatomic species susceptible to only one chemical formula and its reverse e.g., N2 ? N + N and N + N ? N2 (dissociation and recombination). Because of its simplicity, the Lighthill-Freeman model is a useful pedagogical tool, but is unfortunately too simple for modelling non-equilibrium air. Air is typically assumed to have a mole fraction composition of 0.7812 molecular nitrogen, 0.2095 molecular oxygen and 0.0093 argon. The simplest real gas model for air is the five species model, which is based upon N2, O2, NO, N, and O. The five species model assumes no ionization and ignores trace species like carbon dioxide.

When running a Gibbs free energy equilibrium program, [ clarification needed ] the iterative process from the originally specified molecular composition to the final calculated equilibrium composition is essentially random and not time accurate. With a non-equilibrium program, the computation process is time accurate and follows a solution path dictated by chemical and reaction rate formulas. The five species model has 17 chemical formulas (34 when counting reverse formulas). The Lighthill-Freeman model is based upon a single ordinary differential equation and one algebraic equation. The five species model is based upon 5 ordinary differential equations and 17 algebraic equations. [ citation needed ] Because the 5 ordinary differential equations are tightly coupled, the system is numerically "stiff" and difficult to solve. The five species model is only usable for entry from low Earth orbit where entry velocity is approximately 7.8 km/s (28,000 km/h 17,000 mph). For lunar return entry of 11 km/s, [20] the shock layer contains a significant amount of ionized nitrogen and oxygen. The five-species model is no longer accurate and a twelve-species model must be used instead. Atmospheric entry interface [ clarification needed ] velocities on a Mars–Earth trajectory are on the order of 12 km/s (43,000 km/h 27,000 mph). [21] Modeling high-speed Mars atmospheric entry—which involves a carbon dioxide, nitrogen and argon atmosphere—is even more complex requiring a 19-species model. [ citation needed ]

#### Frozen gas model Edit

The frozen gas model describes a special case of a gas that is not in equilibrium. The name "frozen gas" can be misleading. A frozen gas is not "frozen" like ice is frozen water. Rather a frozen gas is "frozen" in time (all chemical reactions are assumed to have stopped). Chemical reactions are normally driven by collisions between molecules. If gas pressure is slowly reduced such that chemical reactions can continue then the gas can remain in equilibrium. However, it is possible for gas pressure to be so suddenly reduced that almost all chemical reactions stop. For that situation the gas is considered frozen. [ citation needed ]

The distinction between equilibrium and frozen is important because it is possible for a gas such as air to have significantly different properties (speed-of-sound, viscosity etc.) for the same thermodynamic state e.g., pressure and temperature. Frozen gas can be a significant issue in the wake behind an entry vehicle. During reentry, free stream air is compressed to high temperature and pressure by the entry vehicle's shock wave. Non-equilibrium air in the shock layer is then transported past the entry vehicle's leading side into a region of rapidly expanding flow that causes freezing. The frozen air can then be entrained into a trailing vortex behind the entry vehicle. Correctly modelling the flow in the wake of an entry vehicle is very difficult. Thermal protection shield (TPS) heating in the vehicle's afterbody is usually not very high, but the geometry and unsteadiness of the vehicle's wake can significantly influence aerodynamics (pitching moment) and particularly dynamic stability. [ citation needed ]

A thermal protection system, or TPS, is the barrier that protects a spacecraft during the searing heat of atmospheric reentry. A secondary goal may be to protect the spacecraft from the heat and cold of space while in orbit. Multiple approaches for the thermal protection of spacecraft are in use, among them ablative heat shields, passive cooling, and active cooling of spacecraft surfaces.

## CONCERNING NASA’S “INGENUITY” MARS HELICOPTER

This is a strange story, one that, perhaps, raises some questions. It was shared by a few regular readers of this website, and concern's NASA's "Ingenuity helicopter," a light weight Mars probe that, in effect, is a helicopter drone designed to fly in the very thin Martian atmosphere:

It's the third article, that from Natural News, that raises the question that was on everyone's mind who sent me the article:

NASA just announced they’ve landed a helicopter on Mars. Known as Ingenuity, the helicopter is now “reporting” from the Red Planet and, we are told, is flying around there. (See Space.com article here.)

The obvious problem with this news, of course, is that Mars has virtually no atmosphere according to official NASA figures, which state the Mars atmosphere is 0.6% the pressure of Earth’s atmosphere. Notably, helicopters can’t fly in a near-vacuum, even in the lower Mars gravity (which is 38% of Earth’s gravity, roughly).

So either NASA is completely lying to us about a helicopter on Mars, or Mars actually has a much thicker atmosphere than 0.6%. For a helicopter to be able to fly around on Mars, the atmosphere would have to be thick enough to breathe, assuming the atmospheric chemistry were compatible with whatever being was engaged in respiration.

But if one reads the CBS article, there's a partial explanation:

Ingenuity is essentially a test flight — it's experimenting with flight on another planet for the first time, and has limited capabilities. It weighs only about 4 pounds, but its success will no doubt pave the way for more ambitious exploration of the red planet.

.

Mars' thin atmosphere, which is 99% less dense than Earth's, will make it difficult for Ingenuity to achieve enough lift to properly fly. Because of this, it has been designed to be extremely lightweight. It stands just 19 inches tall.

The helicopter has four large carbon-fiber blades, fashioned into two rotors that span about 4 feet and spin in opposite directions at about 2,400 rpm — significantly faster than typical helicopters on Earth. (Boldface emphasis added)

It's not only the lightweight that I suspect is at the heart of Ingenuity's success, but those rapidly spinning counter-rotating blades. The famous Russian Tupolev-95 "Bear" bomber, Russia's version of the B-52 strategic bomber, and like the B-52, in service continuously since the 1950s, is by most reports capable of a maximum altitude of about 40,000 feet, remarkable, because the Bear bomber is a prop-driven aircraft, utilizing a design of counter-rotating propellers (a design, incidentally, of German origin). Granted, the air at 40,000 feet is still denser than the almost non-existent Martian atmosphere, but nonetheless, that's a remarkable achievement for a propeller driven aircraft, particularly such a large one, and counter-rotation of the propeller blades is one reason it is able to accomplish such an altitude. One may infer that the Tupolev's maximum altitude is probably even higher.

So, unlike those who sent this story to me and who raised a similar question as that of Natural News, I do not have difficulty believing that the little Ingenuity helicopter may be able to fly around Mars. In fact, the little helicopter was apparently successfully tested in Martian-like atmospheric and gravity conditions. (See https://en.wikipedia.org/wiki/Mars_Helicopter_Ingenuity where we read "In 2019, preliminary designs of Ingenuity were tested on Earth in simulated Mars atmospheric and gravity conditions. For flight testing, a large vacuum chamber was used to simulate the very low atmospheric pressure of Mars – filled with carbon dioxide to approximately 0.60% of standard atmospheric pressure at sea level on Earth – which is roughly equivalent to a helicopter flying at 34,000 m (112,000 ft) altitude in the atmosphere of Earth. In order to simulate the much reduced gravity field of Mars, 62% of Earth's gravity was offset by a line pulling upwards during flight tests.")

I suspect, rather, that there's a very different story here than that of any NASA conspiracy to obfuscate the level of atmospheric pressure on Mars, and I suspect that story has very much to do with the long-term implications of Ingenuity. As the Wikipedia story indicates, Ingenuity is a "proof-of-concept" experiment, which now appears to have been successful:

Ingenuity is designed to be a technology demonstrator by JPL to assess whether this technology can fly safely, and provide better mapping and guidance that would give future mission controllers more information to help with travel routes planning and hazard avoidance, as well as identifying points of interest for the rover. [14] [15] [16] The helicopter is designed to provide overhead images with approximately ten times the resolution of orbital images, and will provide images of features that may be occluded from the cameras of the Perseverance rover. [17] It is expected that such scouting may enable future rovers to safely drive up to three times as far per sol. (Boldface emphasis added)

In other words, imagine scaling Ingenuity up, to a scale that it could support a variety of cameras and sensors, with "overhead images approximately ten times the resolution of orbital images," and you get the picture, so to speak. Given all the strange stuff - from things that look like fossils to things that look not only machined but like machines - that has been photographed by satellites and surface probes on Mars, it would appear that the real story behind Ingenuity is that NASA wants to get a "closer look" at that strange stuff. In other words, stay tuned. there's more to come.

### 31 thoughts on &ldquoCONCERNING NASA’S “INGENUITY” MARS HELICOPTER&rdquo

A 4 foot rotor turning at 2400 rpm is perfectly reasonable. Light aircraft propellers are 5 to 6 feet in diameter and are typically operated between 2000 and 2700 rpm. Propeller RPM is normally limited by the speed of the propeller tips which needs to be below about 0.9 mach to be efficient. A full sized helicopter rotor turns at a much lower rpm due to the much larger diameter of the rotor.

Mars….Smaars!! We have had a base on Mars since the 80’s at least!! I remember one Wh.bl. telling how he had to wear a bio-suit & how when it snowed, the birds would come out of a cave. There were battles between the various ones who had bases there & if they could get to a wounded warrior in time to save even a smidgen piece, that warrior could be “remade”!! Talk about tech that has been hidden from us.

Another Wh.bl told of going into an elevator, was told to press a certain button & when the door opened on the opposite side. he was on Mars!! When will this illusion we live in FINALLY be smashed.

Billy Carson has excellent photos of what has been found on Mars. For any wishing an update on our present situation….check out Martin Geddes latest newsletter!! He puts things in a concise & logical manner!!

Don’t you love old photos? I remember in the late seventies Venus photos showed it to be a blue water world which got people all excited so they claimed that was just the result of a filter they used and it was really cloudy sulfuric yellow looking. Mars looks to have quite the dynamic atmosphere according to Hubble. http://www.twoplanetsteel.com/images/news/Mars.seasonal.comparison.jpg

Could be the Russians set off an experimental neutron bomb on Venus which caused it to resurface and change colors. You deffinately would not want to test it on Earth and it was the seventies and the cold war still raged. Russia was sending all kinds of stuff to Venus while the west distracted us with Mars.

I expect the Russians were clearing out Maria Orsic’s ‘Space Brothers’ Nazi outpost on Venus. Only half joking…

Must have been fun matching blade span, width, pitch, rotation rate per minute, and material construction on that craft to gain a calculated height off the surface of very low atmospheric density.

More & more moves like these worldwide will create a tidal change
Mr. Globaloney will be caught naked in, as the tide moves outwards.

2020 saw humanity being set an Advanced Gullibility Test – which it passed with flying colours! BUT public opinion is a supertanker… and if it starts to turn…

Apparently the funny pages have move to the front folds of the news.
Turn on the news read the headlines all are comical in that they want you, to take them seriously. Talk about crazy conspiracies!
Just read, and/or watch the news!
You’ve got to wonder?
Do they actually believe their own press?

Wonder if that drone is going to do a flyby Cydonia and have another look at that face…….whoops

Capricon One anyone though I have never seen the movie I saw a made for tv movie variant about a man Mars mission gone bad where the astronaut dies and NASA has to use a body double to cover up his death. Given all the endemic lying and making things up in this society do we really know what is true and real anymore as Richard Hoagland says NASA stands for never a straight answer. As one of the commentators on this post has written NASA may be using suppress technology to make the Marscopter work in that thin atmosphere.

If we find Mars has no life I propose we introduce lichens and bacteria that will release nitrogen gas from the Martian soil and convert CO2 to oxygen. https://www.astrobio.net/extreme-life/lichen-on-mars/

I for one don’t think Mars ever had standing water in it’s past unless a meteor crashed into a glacier or volcanism in the past erupted under a polar glacier. Not enough gravity or atmosphere. Now Venus I suspect had life, and not too long ago cosmoligically speaking anyways. And I would begin terra forming it rather than Mars. First I would introduce high temp and pressure tollerant sulfur loving bacteria. Maybe a GMO created one that would rapidly multiply and cover the surface of Venus and begin breaking down sulfuric acid and CO2 as well as release nitrogen gas.

I suppose if Mars shifts enough in its rotation to where polar glaciers get more equatorial located they could melt during the day but would evaporate and get redeposited in the new polar surface location.

The video I saw looked like a Hollywood stage production. The videos attached to the article appear smaller. Call me cynical, but how do we even know these people are real scientists and not professional actors? Either that–or today’s scientist actually “looks” better than those of 50 years ago.

*Hat tip to Radio Far Side

Chan Thomas’ Adam and Eve Story talks about cyclical cataclysms caused by Stellar conditions (independently found by Paul la Violette and his super wave theory) inducing crustal displacement.

Earths ionosphere partially masks the early phase of these events, I’m guessing the thin atmosphere of Mars is the perfect place to measure this.

So the Mars missions might be about something altogether different than the standard story. Pretty pictures are a side show.

Nice catch. Reread this one. Seems like Ingenuity tech will get used above Earth more often. How long can a solar powered unit stay above 40k feet looking down getting and sending better and cheaper and quicker images than satellites orbiting higher?

We might speculate that the “Cosmic War” is still on (nothing new for Giza fans) and that this drone may actually have military purposes, with respect to parties currently present on Malacandra, whether hailing from Earth or from Elsewhere.

It sure is still on!
That’s a perspective I should have immediately thought of
given how Mar’s moon Phobias seems to be somewhat deadly,
when certain parameters are crossed.
[perhaps programmed?]

Trust the AI?
Trust the scientists/leadership on their perceptions?
How many actually decided mankind was obsolete
and had to go the way of the Dodo?
An insane asylum is deciding the fate of mankind?
Or, believing antique AI’s: “Facts? Futures? Conclusions? & What nots”.

Is the Mars “helicopter” using some Von Braun off-the-moon technology?

Your further explanations signal that the technology of counter rotation and other factors make this helicopter proof of concept believable.

The Natural News story is The Story.
As if the posthuman AIs conclusions of mankind were a given.

“Moon Shmoon” said Werner Von Braun.

The atmosphere over Devon Island is remarkably similar to that of the rest of the planet, and thus is unlikely to pose significant problems for the “Mars” drone aerofoils…. Perhaps we’ll eventually get some more excellent shots of the Arctic Lemming, fossil crinoids, or other elements indigenous to the highly restricted, largest uninhabited island in the world where Nasa “tests” its props.

Exciting stuff, but wonder if we’ll ever see the photos? They won’t even tell us what’s in Antarctica!

I had to dig up an old computer and boot it up to find this information for you, hope you like it.

You say “there’s a very different story here than that of any NASA conspiracy to obfuscate the level of atmospheric pressure on Mars,” but there is ample documentation that THAT is exactly what NASA has been doing for many years now.

Here’s a 223 page report on exactly that:

ABSTRACT: We present evidence that NASA is seriously understating Martian air pressure.
Our 10-year study critiques 2,676 Sols (

7.53 terrestrial years, 4 Martian years) of highly
problematic MSL Rover Environmental Monitoring Station (REMS) weather data, and offers
an in depth audit of over 8,311 hourly Viking 1 and 2 weather reports. We discuss analysis of
technical papers, NASA documents, and personal interviews of transducer designers. We
troubleshoot pressures based on radio occultation/spectroscopy, and the previously accepted
small pressure ranges that could be measured by Viking 1 and 2 (18 mbar), Pathfinder and
Phoenix (12 mbar), and MSL (11.5 mbar – altered to 14 mbar in 2017). For MSL there were
several pressures published from August 30 to September 5, 2012 that were from 737 mbar to
747 mbar – two orders of magnitude high – only to be retracted. We challenged many pressures
and NASA revised them down. However there are two pressure sensors ranges listed on a
CAD for Mars Pathfinder. We long thought the CAD listed two different sensors, but based
on specifications of a new Tavis sensor for InSight that is like that on PathFinder, it appears
that the transducer could toggle between two pressures ranges: 0-0.174 PSIA/12 mbar (Tavis
Dash 2) and 0-15 PSIA/1,034 mbar (Tavis Dash 1). Further, for the MSL according to an
Abstract to the American Geophysical Union for the Fall 2012 meeting, The Finnish
Meteorological Institute (FMI) states of their MSL (and Phoenix) Vaisala transducers, “The
pressure device measurement range is 0 – 1025 hPa in temperature range of -45°C – +55°C (-
45°C is much warmer than MSL night temperatures), but its calibration is optimized for the
Martian pressure range of 4 – 12 hPa.” So while we first thought that of the first five landers
that had meteorological suites, none could measure Earth-like pressures, in fact, three landers
were actually equipped to get the job. Further, all original 19 low UV values were removed
when we asked about them, although they eventually restored 12 of them. REMS always-sunny
opacity reports were contradicted by Mars Reconnaissance Orbiter photos. Why REMS Team
data was so wrong is a matter of speculation, but we demonstrate that their weather data was
regularly revised after they studied online critiques in working versions of this report. REMS
even labelled all dust 2018 Global Dust Storm weather as sunny, although they did list the UV
values then as all low.
Vikings and MSL showed consistent timing of daily pressure spikes which we link to how gas
pressure in a sealed container would vary with Absolute temperature, to heating by
radioisotope thermoelectric generators (RTGs), and to dust clots at air access tubes and dust
filters. Pathfinder, Phoenix and MSL wind measurements failed. Phoenix and MSL pressure
transducer design problems included confusion about dust filter location, and lack of
information about nearby heat sources due to International Traffic and Arms Regulations
(ITAR). NASA Ames could not replicate dust devils at 10 mbar. Rapidly filled MER Spirit
tracks required wind speeds of 80 mph at the assumed low pressures. These winds were never
recorded on Mars. Nor could NASA explain drifting Barchan sand dunes. Based on the above
and dust devils on Arsia Mons to altitudes of 17 km above areoid (Martian equivalent of sea
level), spiral storms with 10 km eye-walls above Arsia Mons and similar storms above
Olympus Mons (over 21 km high), dust storm opacity at MER Opportunity blacking out the
sun, snow that descends 1 to 2 km in only 5 or 10 minutes, excessive aero braking, liquid water
running on the surface in numerous locations at Recurring Slope Lineae (RSL) and stratus
clouds 13 km above areoid, we argue for an average pressure at areoid of

511 mbar rather
than the accepted 6.1 mbar. This pressure grows to 1,050 mbar in the Hellas Basin.

## Mars terraforming not possible using present-day technology

This infographic shows the various sources of carbon dioxide on Mars and their estimated contribution to Martian atmospheric pressure. Credit: NASA

Science fiction writers have long featured terraforming, the process of creating an Earth-like or habitable environment on another planet, in their stories. Scientists themselves have proposed terraforming to enable the long-term colonization of Mars. A solution common to both groups is to release carbon dioxide gas trapped in the Martian surface to thicken the atmosphere and act as a blanket to warm the planet.

However, Mars does not retain enough carbon dioxide that could practically be put back into the atmosphere to warm Mars, according to a new NASA-sponsored study. Transforming the inhospitable Martian environment into a place astronauts could explore without life support is not possible without technology well beyond today's capabilities.

Although the current Martian atmosphere itself consists mostly of carbon dioxide, it is far too thin and cold to support liquid water, an essential ingredient for life. On Mars, the pressure of the atmosphere is less than one percent of the pressure of Earth's atmosphere. Any liquid water on the surface would very quickly evaporate or freeze.

Proponents of terraforming Mars propose releasing gases from a variety of sources on the Red Planet to thicken the atmosphere and increase the temperature to the point where liquid water is stable on the surface. These gases are called "greenhouse gases" for their ability to trap heat and warm the climate.

"Carbon dioxide (CO2) and water vapor (H2O) are the only greenhouse gases that are likely to be present on Mars in sufficient abundance to provide any significant greenhouse warming," said Bruce Jakosky of the University of Colorado, Boulder, lead author of the study appearing in Nature Astronomy July 30.

Although studies investigating the possibility of terraforming Mars have been made before, the new result takes advantage of about 20 years of additional spacecraft observations of Mars. "These data have provided substantial new information on the history of easily vaporized (volatile) materials like CO2 and H2O on the planet, the abundance of volatiles locked up on and below the surface, and the loss of gas from the atmosphere to space," said co-author Christopher Edwards of Northern Arizona University, Flagstaff, Arizona.

The researchers analyzed the abundance of carbon-bearing minerals and the occurrence of CO2 in polar ice using data from NASA's Mars Reconnaissance Orbiter and Mars Odyssey spacecraft, and used data on the loss of the Martian atmosphere to space by NASA's MAVEN (Mars Atmosphere and Volatile Evolution) spacecraft.

"Our results suggest that there is not enough CO2 remaining on Mars to provide significant greenhouse warming were the gas to be put into the atmosphere in addition, most of the CO2 gas is not accessible and could not be readily mobilized. As a result, terraforming Mars is not possible using present-day technology," said Jakosky.

Although Mars has significant quantities of water ice that could be used to create water vapor, previous analyses show that water cannot provide significant warming by itself temperatures do not allow enough water to persist as vapor without first having significant warming by CO2, according to the team. Also, while other gases such as the introduction of chloroflorocarbons or other fluorine-based compounds have been proposed to raise the atmospheric temperature, these gases are short-lived and would require large-scale manufacturing processes, so they were not considered in the current study.

The atmospheric pressure on Mars is around 0.6 percent of Earth's. With Mars being further away from the Sun, researchers estimate a CO2 pressure similar to Earth's total atmospheric pressure is needed to raise temperatures enough to allow for stable liquid water. The most accessible source is CO2 in the polar ice caps it could be vaporized by spreading dust on it to absorb more solar radiation or by using explosives. However, vaporizing the ice caps would only contribute enough CO2 to double the Martian pressure to 1.2 percent of Earth's, according to the new analysis.

Another source is CO2 attached to dust particles in Martian soil, which could be heated to release the gas. The researchers estimate that heating the soil could provide up to 4 percent of the needed pressure. A third source is carbon locked in mineral deposits. Using the recent NASA spacecraft observations of mineral deposits, the team estimates the most plausible amount will yield less than 5 percent of the required pressure, depending on how extensive deposits buried close to the surface may be. Just using the deposits near the surface would require extensive strip mining, and going after all the CO2 attached to dust particles would require strip mining the entire planet to a depth of around 100 yards. Even CO2 trapped in water-ice molecule structures, should such "clathrates" exist on Mars, would likely contribute less than 5 percent of the required pressure, according to the team.

Carbon-bearing minerals buried deep in the Martian crust might hold enough CO2 to reach the required pressure, but the extent of these deep deposits is unknown, not evidenced by orbital data, and recovering them with current technology is extremely energy intensive, requiring temperatures above 300 degrees Celsius (over 572 degrees Fahrenheit). Shallow carbon-bearing minerals are not sufficiently abundant to contribute significantly to greenhouse warming, and also require the same intense processing.

Although the surface of Mars is inhospitable to known forms of life today, features that resemble dry riverbeds and mineral deposits that only form in the presence of liquid water provide evidence that, in the distant past, the Martian climate supported liquid water at the surface. But solar radiation and solar wind can remove both water vapor and CO2 from the Martian atmosphere. Both MAVEN and the European Space Agency's Mars Express missions indicate that the majority of Mars' ancient, potentially habitable atmosphere has been lost to space, stripped away by solar wind and radiation. Of course, once this happens, that water and CO2 are gone forever. Even if this loss were prevented somehow, allowing the atmosphere to build up slowly from outgassing by geologic activity, current outgassing is extremely low it would take about 10 million years just to double Mars' current atmosphere, according to the team.

Another idea is to import volatiles by redirecting comets and asteroids to hit Mars. However, the team's calculations reveal that many thousands would be required again, not very practical.

Taken together, the results indicate that terraforming Mars cannot be done with currently available technology. Any such efforts have to be very far into the future.

## At what depth on Mars would the atmosphere have equal pressure of that on Earth? - Astronomy

The Martian atmosphere is an extremely thin sheet of gas, principally carbon dioxide, that extends from the surface of Mars to the edge of space. The Martian atmosphere is less dense than the Earth's atmosphere, but there are many similarities. Gravity holds the atmosphere to the Martian surface. Within the atmosphere, very complex chemical, thermodynamic, and fluid dynamics effects occur. The atmosphere is not uniform fluid properties are constantly changing with time and place, producing weather on Mars just like on Earth.

Variations in atmospheric properties extend upward from the surface of Mars. The sun heats the surface, and some of this heat goes into warming the gas near the surface. The heated gas is then diffused or convected up through the atmosphere. Thus, the gas temperature is highest near the surface and decreases as altitude increases. The speed of sound depends on the temperature and also decreases with increasing altitude. As with the Earth, the pressure in the atmosphere decreases with altitude. The density of the atmosphere depends on both the temperature and the pressure through the equation of state and also decreases with increasing altitude.

Aerodynamic forces directly depend on the gas density. To help spacecraft designers, it is useful to define a mathematical model of the atmosphere to capture the effects of altitude. The model shown here was developed from measurements of the Martian atmosphere made by the Mars Global Surveyor in April 1996. The information on the Martian atmosphere was gathered by Jonathon Donadee of Canfield (Ohio) Middle School during a cyber-mentoring program in 1999. The data was curve fit to produce equations by Dave Hiltner of St. John's Jesuit High School as part of a shadowing program in May 1999. The curve fits are given for Imperial units. These curve fits are also available in metric units.

The model has two zones with separate curve fits for the lower atmosphere and the upper atmosphere. The lower atmosphere runs from the surface of Mars to 22,960 feet. In the lower atmosphere, the temperature decreases linearly and the pressure decreases exponentially. The rate of temperature decrease is called the lapse rate. For the temperature T and the pressure p, the Imperial units curve fits for the lower atmosphere are:

where the temperature is given in Fahrenheit degrees, the pressure in pounds/square feet, and h is the altitude in feet. The upper stratosphere model is used for altitudes above 22,960 feet. In the upper atmosphere the temperature decreases linearly and the pressure decreases exponentially. The Imperial units curve fits for the upper atmosphere are:

In each zone the density r is derived from the equation of state.

Comparing this equation with the similar equation of state for the Earth's atmosphere, you will notice that the gas constants are different, 1149 for Mars and 1718 for Earth. These numbers are different because the Martian atmosphere is almost entirely composed of carbon dioxide, while the Earth's atmosphere is a mixture of 78% nitrogen and 21% oxygen.

This is the atmosphere model used in the FoilSim simulator. The model is also available in an interactive atmosphere simulation program. With the applet, you can change altitude and see the effects on pressure and temperature. You can also compare the Martian atmosphere to the atmosphere on Earth.