Can Humans Live on Mars?

by Ken Kremer on November 19, 2012

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Image caption: Curiosity is taking the first ever radiation measurements from the surface of another planet in order to determine if future human explorers can live on Mars – as she traverses the terrain of the Red Planet. Curiosity is looking back to her rover tracks and the foothills of Mount Sharp and the eroded rim of Gale Crater in the distant horizon on Sol 24 (Aug. 30, 2012). This panorama is featured on PBS NOVA ‘Ultimate Mars Challenge’ documentary which premiered on PBS TV on Nov. 14. RAD is located on the rover deck in this colorized mosaic stitched together from Navcam images by the image processing team of Ken Kremer & Marco Di Lorenzo. Credit: NASA / JPL-Caltech / Ken Kremer / Marco Di Lorenzo

Metallic robots constructed by ingenious humans can survive on Mars. But what about future human astronauts?

NASA’s plucky Mars Exploration Rover Opportunity has thrived for nearly a decade traversing the plains of Meridiani Planum despite the continuous bombardment of sterilizing cosmic and solar radiation from charged particles thanks to her radiation hardened innards.

How about humans? What fate awaits them on a bold and likely year’s long expedition to the endlessly extreme and drastically harsh environment on the surface of the radiation drenched Red Planet - if one ever gets off the ground here on Earth? How much shielding would people need?

Answering these questions is one of the key quests ahead for NASA’s SUV sized Curiosity Mars rover – now 100 Sols, or Martian days, into her 2 year long primary mission phase.

Preliminary data looks promising.

Curiosity survived the 8 month interplanetary journey and the unprecedented sky crane rocket powered descent maneuver to touch down safely inside Gale Crater beside the towering layered foothills of 3 mi. (5.5 km) high Mount Sharp on Aug. 6, 2012.

Now she is tasked with assessing whether Mars and Gale Crater ever offered a habitable environment for microbial life forms – past or present. Characterizing the naturally occurring radiation levels stemming from galactic cosmic rays and the sun will address the habitability question for both microbes and astronauts. Radiation can destroy near-surface organic molecules.

Researchers are using Curiosity’s state-of-the-art Radiation Assessment Detector (RAD) instrument to monitor high-energy radiation on a daily basis and help determine the potential for real life health risks posed to future human explorers on the Martian surface.

“The atmosphere provides a level of shielding, and so charged-particle radiation is less when the atmosphere is thicker,” said RAD Principal Investigator Don Hassler of the Southwest Research Institute in Boulder, Colo. See the data graphs herein.

“Absolutely, the astronauts can live in this environment. It’s not so different from what astronauts might experience on the International Space Station. The real question is if you add up the total contribution to the astronaut’s total dose on a Mars mission can you stay within your career limits as you accumulate those numbers. Over time we will get those numbers,” Hassler explained.

The initial RAD data from the first two months on the surface was revealed at a media briefing for reporters on Thursday, Nov. 15 and shows that radiation is somewhat lower on Mars surface compared to the space environment due to shielding from the thin Martian atmosphere.

Image caption: Longer-Term Radiation Variations at Gale Crater. This graphic shows the variation of radiation dose measured by the Radiation Assessment Detector on NASA’s Curiosity rover over about 50 sols, or Martian days, on Mars. (On Earth, Sol 10 was Sept. 15 and Sol 60 was Oct. 6, 2012.) The dose rate of charged particles was measured using silicon detectors and is shown in black. The total dose rate (from both charged particles and neutral particles) was measured using a plastic scintillator and is shown in red. Credit: NASA/JPL-Caltech/ SwRI

RAD hasn’t detected any large solar flares yet from the surface. “That will be very important,” said Hassler.

“If there was a massive solar flare that could have an acute effect which could cause vomiting and potentially jeopardize the mission of a spacesuited astronaut.”

“Overall, Mars’ atmosphere reduces the radiation dose compared to what we saw during the cruise to Mars by a factor of about two.”

RAD was operating and already taking radiation measurements during the spacecraft’s interplanetary cruise to compare with the new data points now being collected on the floor of Gale Crater.

Mars atmospheric pressure is a bit less than 1% of Earth’s. It varies somewhat in relation to atmospheric cycles dependent on temperature and the freeze-thaw cycle of the polar ice caps and the resulting daily thermal tides.

“We see a daily variation in the radiation dose measured on the surface which is anti-correlated with the pressure of the atmosphere. Mars atmosphere is acting as a shield for the radiation. As the atmosphere gets thicker that provides more of a shield. Therefore we see a dip in the radiation dose by about 3 to 5%, every day,” said Hassler.

Image Caption: Curiosity Self Portrait with Mount Sharp at Rocknest ripple in Gale Crater. Curiosity used the Mars Hand Lens Imager (MAHLI) camera on the robotic arm to image herself and her target destination Mount Sharp in the background. Mountains in the background to the left are the northern wall of Gale Crater. This color panoramic mosaic was assembled from raw images snapped on Sol 85 (Nov. 1, 2012). Credit: NASA/JPL-Caltech/MSSS/Ken Kremer/Marco Di Lorenzo

There are also seasonal changes in radiation levels as Mars moves through space.

The RAD team is still refining the radiation data points.

“There’s calibrations and characterizations that we’re finalizing to get those numbers precise. We’re working on that. And we’re hoping to release that at the AGU [American Geophysical Union] meeting in December.”

Image caption: Daily Cycles of Radiation and Pressure at Gale Crater. This graphic shows the daily variations in Martian radiation and atmospheric pressure as measured by NASA’s Curiosity rover. As pressure increases, the total radiation dose decreases. When the atmosphere is thicker, it provides a better barrier with more effective shielding for radiation from outside of Mars. At each of the pressure maximums, the radiation level drops between 3 to 5 percent. The radiation level goes up at the end of the graph due to a longer-term trend that scientists are still studying. Credit: NASA/JPL-Caltech/SwRI

Radiation is a life limiting factor to habitability. RAD is the first science instrument to directly measure radiation from the surface of a planet other than Earth.

“Curiosity is finding that the radiation environment on Mars is sensitive to Mars weather and climate,” Hassler concluded.

Unlike Earth, Mars lost its magnetic field some 3.5 billion years ago – and therefore most of its shielding capability from harsh levels of energetic particle radiation from space.

Much more data will need to be collected by RAD before any final conclusions on living on Mars, and for how long and in which type habitats, can be drawn.

Learn more about Curiosity and NASA missions at my upcoming free public presentations:

- – on Dec. 6 held at Brookdale Community College, Monmouth Museum, Lincroft, NJ at 8 PM – hosted by STAR astronomy

- – and on Dec 11 held at Princeton University and the Amateur Astronomers Association of Princeton (AAAP) in Princeton, NJ at 8 PM.

And be sure to watch the excellent PBS NOVA Mars documentary – ‘Ultimate Mars Challenge’ - which also features Curiosity mosaics created by the imaging team of Ken Kremer & Marco Di Lorenzo.

Ken Kremer


Dec 6: Free Public lecture titled “Atlantis, The Premature End of America’s Shuttle Program and What’s Beyond for NASA” including Curiosity, Orion, SpaceX and more by Ken Kremer at Brookdale Community College/Monmouth Museum and STAR Astronomy club in Lincroft, NJ at 8 PM

Dec 11: Free Public lecture titled “Curiosity and the Search for Life on Mars (in 3 D)” and more by Ken Kremer at Princeton University and the Amateur Astronomers Association of Princeton (AAAP) in Princeton, NJ at 8 PM.


Dr. Ken Kremer is a speaker, scientist, freelance science journalist (Princeton, NJ) and photographer whose articles, space exploration images and Mars mosaics have appeared in magazines, books, websites and calanders including Astronomy Picture of the Day, NBC, BBC,, Spaceflight Now and the covers of Aviation Week & Space Technology, Spaceflight and the Explorers Club magazines. Ken has presented at numerous educational institutions, civic & religious organizations, museums and astronomy clubs. Ken has reported first hand from the Kennedy Space Center, Cape Canaveral and NASA Wallops on over 40 launches including 8 shuttle launches. He lectures on both Human and Robotic spaceflight -

Jose Saez November 19, 2012 at 4:38 AM

I’d love to go there myself. If there’s no life on Mars, we should start bombing the planet with ice asteroids, moving dust around and generating a little global warming. We can do it.

Steve Kruckheimmer November 19, 2012 at 9:39 PM

What have humans ever done that would lead you to conclude that we either have this capability (to bomb another planet with ice asteroids), or should do it? That’s like thinking you can punch someone in the face and they would end up more attractive, or somehow better off, than before.

lcrowell November 21, 2012 at 2:55 PM

That is the rub; the law of unexpected consequences. Even here on Earth with our far more modest environmental modification efforts we find we are changing the chemistry of the atmosphere and perturbing other chemical and biological cycles. Of course bombing Mars with comets or asteroid ice would change things, but it might not be how one expected.

I am not sure about the future of human habitation in space. However, I think if this development takes place I think we are far more likely to convert asteroids into mini-habitats rather than terraforming enclosed regions on planets. A hollowed out asteroid could make a fair habitat with solid shielding and where the whole thing is rotating to create pseudo-gravity inside.


M Peter Selman November 20, 2012 at 9:03 AM

Excuse me for being a nitpick, but as far as I read, bolide impacts and kicking off dust are associated with an ‘unhelpful’ cooling effect. Robert Zubrin suggested impacting massive ammonia rich objects into the southern polar cap. A double whammy, blasting green-house producing CO2 and ammonia into the atmosphere. It could take a prolonged series of bombardments to have desirable pressures and conditions. Though it is said the energy released could prevent any settlement for a long time. Though I do wonder by increasing atmospheric pressure, might we increase dust lifting, thereby exacerbate seasonal dust storms, creating another cooling effect? It would be a while until enough pressure and heat exists for a water cycle and trap the dust into mud and clay.

massmurdoch November 19, 2012 at 7:27 AM

I guess this means that, at any really unlucky moment, our lunar astronauts could have found themselves whacked by a solar flare and vomiting in the suit. Never thought about that.

Torbjörn Larsson November 19, 2012 at 10:31 AM

It has been voiced as a concern for manned missions during arrival and departure. Both as the debilitation as the accumulated dose grows and in case a CME would hit at a critical moment for a crew. (Not that vomiting from space sickness isn’t an ongoing concern.)

Where is HAL 9000 when you need him?

newSteveZodiac November 19, 2012 at 1:51 PM

The vomiting takes a while to start, enough rads to start immediately and you’d be dead immediately.

M Peter Selman November 20, 2012 at 9:08 AM

Solar observation and space weather forecasting can give enough time and warning to enter a shelter.

massmurdoch November 20, 2012 at 5:46 PM

As we evolve as a species, I suspect abdominal vomit vents are coming, which will make suit design easier.

M Peter Selman November 21, 2012 at 11:18 AM

No more adult diapers, yes*.

Torbjörn Larsson November 19, 2012 at 10:22 AM

An overall factor of 2 less is not bad, as a comparison a craft wall at ~ 10 g/cm^2 Al would cut solar wind proton radiation with a factor ~ 10 (table 27, p 139) . A suit with < 1 g/cm^2 Al (ibid, p 132) would cut solar protons a mere ~ 20 %, so the martian atmosphere is the dominant protection outside vehicles.

The atmosphere would do even better at impactors, so this is a definite win.

Unlike Earth, Mars lost its magnetic field some 3.5 billion years ago – and therefore most of it’s shielding capability from harsh levels of energetic particle radiation from space.

Well, it is the lost atmosphere that means most in the form of a shield lost. Earth atmosphere stops most of the cosmic radiation. And it would stop solar wind protons if they got past the magnetic field as demonstrated by the martian atmosphere stopping power.

But Earth magnetic shield protects the ISS crews from most of the solar wind effects, so we have lost that additional shield as well.

lcrowell November 19, 2012 at 7:59 PM

The collapse of the magnetic field on Mars meant the atmosphere was impacted by solar wind and CMEs. This in effect blew much of the atmosphere away. If Earth lost its magnetic field there might be a similar effect. It effected Mars in particular because it has weak gravity that has less hold on its atmosphere


Hans Peter Uhrig November 20, 2012 at 10:28 AM

Venus got essentual no magnetic field but a massive atmosphere while Titan (Saturns moon) has less gravity than Mars and also sports a dense atmosphere. This should be something to think about the current paradigms/dogmas in planetary science.
But the most interesting part is that another more or less dogmatic view of a deadly Martian surface has been dealt a critical blow. Does anybody still think hardy microbial life is not possible on/near Mars’ surface? It should therefore now be “more easy” to accept the possibility that the Viking biology experiments detected signs of (microbial) life among some chemical noise. Especially the Viking LR data could not be any clearer with the setup sent to Mars in regards to microbial metabolic activity in the Martian soil…

lcrowell November 20, 2012 at 4:27 PM

There are a number of things one can reason about conditions on planets. Titan for instance is out around 10 AU, which means solar radiation is 1/100 that on Earth. The temperature is much lower on Titan as a result. The equipartition theorem of thermodynamics says the three degrees of freedom of motion have average energy 1/2mv^2, for v the average velocity of the particles or molecules, and this equals the thermal energy kT. As a result (3/2)mv^2 = kT and the velocity of molecules is v = sqrt{2kT/3m} and is thus much lower. Titan may then be able to hold a thick atmosphere this way. If the average velocity is low there are few molecules with escape velocity.

With Venus it is likely the atmosphere was fairly thick to begin with. When it went into a superhot state all the carbon in rocks boiled off as CO_2. The atmosphere is so thick that it is fairly resilient to solar “evaporation.” Other reasons might be worked out, and of course planets are complicated systems so this is not always straight forwards.

The Viking detection was inconclusive. There are some possible hints that this might have been life. However, the experiment was not properly designed to clearly make a conclusion.

If life exists on Mars it is then probably unwise to perturb the planet with our presence. Life might exist in a liquid water layer on top of subsurface glaciers. The appearance of fluid tracks in gullies from crater sides suggests such liquid may exist. If such life is detected it might behoove us to not contaminate the planet with Earth life, nor would it be wise to inadvertently bring Martian life back to Earth as “invasive species.”


Hans Peter Uhrig November 21, 2012 at 12:10 PM

Regarding Viking there seems to be a massive trained misconception… First of all it was not a single life detection experiment but a set of three not interlinked experiments to approach the search for extraterrestrial life from different angles. One positive result of the three experiments regardless if the other experiments yielded inconclusive or negative results would have been proof of life by Viking mission protocols. Actually this scenario had been the case. One single life detection experiment of the three signaled the presence of life on Mars by causing a consistent (both landing sites) positive result (metabolic reaction) in the active runs and a consistent negative result in the subsequent control runs (heat sterilized controls to exclude purely chemical reactions as has been tested with flight hardware for like a decade prior the mission on Earth). So the problem was not the life detection experiments but the Viking GC/MS which did not find organics so they concluded that Mars’ surface is totally devoid of organics and therefore there can be no life.

But talk is cheap lets wait for the “Earth shaking” discovery of MSL which is announced – I guess it will be somewhat related to Viking… ;-)

Peristroika November 21, 2012 at 4:25 PM

“unwise to perturb the planet with our presence”…why? How would our disturbance of the tenuous martian ecosystem (should there be one) be “unwise”?? It’s probably not in a state of evolution/growth/positive flux. We might not be able to affect it at all (if it isn’t DNA based) nor is our presence ever going to displace much (.0000000138% based on a massive 2 sq km base) of the martian surface. Unwise to a few exoprotozoans or unwise to our nascient politically correct sense of universal propriety?

Steve Kruckheimmer November 25, 2012 at 1:27 AM

What do you mean “An overall factor of 2 less is not bad”? The conditions required to support life are pretty well understood, and pretty intolerant of variation, at least insofar as specific species are concerned.

newSteveZodiac November 19, 2012 at 2:00 PM

Looks promising, we don’t need to gene engineer humans to live on Mars which would slow thngs down even more but we might need to build CME/Flare shelters. .

Steve Kruckheimmer November 19, 2012 at 9:32 PM

Humans on Mars and Earth will evolve in different directions – you could consider this a form of genetic engineering.

lcrowell November 19, 2012 at 7:03 PM

I look upon these things with a certain jaded eye. If you spend enough money and energy you can create the artificial habitats that humans can live in. Even in principle this could be done on Venus, which would be a daunting prospect. However, given sufficient expenditure of resources I am sure it could be achieved. There are some questions concerning why we should do this. I object to the notion that we can demolish Earth with the expectation we can migrate off to other planets. I think that is a false proposition.

It is certainly not “in principle” impossible that we could terraform Mars into something proximal to Earth. It is just a vastly scaled up version of what we already do, such as building green suburban landscapes in the desert complete with 18 hole golf courses. Our species has a remarkable ability to exploit this planet’s resources, and our intelligence gives us the power to figure out new ways to accomplish this and to continually expand our control. These ideas are effectively proposals for doing this off Earth and onto other planets. We might ponder though whether these things are always such a good idea, and whether there are ultimately limits to our ability to control the natural world.

The planets in this solar system evolved into the state they currently have. We might think of this as some huge space of high dimension, each dimension representing some physical parameter, where there are certain basins of attraction. These basins are then homeostatic conditions that environments can exist in. Mars exists in its basin, Venus in its and the same with Earth. In fact all the planets are in some basin. What is then proposed is to interfere with these planets, or some local contained region on them, to knock it out of its current basin and guide it towards another that is more commensurate with Earth. This is a vast complex problem to solve. It also means that structures on a planet, such as maybe life on Mars, will be degraded or demolished. This in the end sounds not that different from things we do locally here on Earth, such as clearing forests to make way for agricultural land, removing mountains to get coal, changing the chemistry of the atmosphere and so forth.

More specifically with respect to radiation, humans can’t live on Mars without appropriate shielding. We have about 1.1kg of matter above every cm^2 us at sea level. To reduce radiation levels you would need at least 10 to 30% of that much material per cm^2 in what ever shell or bubble humans would live in. This also pertains to any interplanetary space craft. The cost would be large in order to change some local “patch” of territory so as to be commensurate with our survival. We need to consider the costs and effectiveness between changing this local environment on Mars contrasted with getting some sort of grip on our uncontrolled experiment that is changing or increasing the entropy of the environment here on Earth.


Steve Kruckheimmer November 19, 2012 at 9:31 PM

Terraforming is not just a vastly scaled up version of what we already do, such as building green suburban landscapes in the desert complete with 18 hole golf courses. Anyone can build a golf course in the desert, it’s simple enough to either build a ditch to carry water or lay pipes to a water source. Terraforming is not a scaled up version of this. A golf course in the desert is hardly analogous to building a colony on Mars. The problem is scientists and engineers are prone to this sort of trivialization.
There’s a difference between getting a man to Mars, just to say we did it, and moving MANKIND to Mars, especially if that also means along with our 21st century standards. A BIG BIG difference that no one seems to be worried about, and which, I believe, is insurmountable.

lcrowell November 19, 2012 at 11:48 PM

It was not possible to build a large green suburbia in the desert 200 years ago. The city of Dubai is a big example of this, and this would not have been possible without modern equipment. The use of large pumps, the power systems to run them, the manufacturing system to construct the steel, plastics and so forth to make this work are all examples of advanced technology. The principles are ultimately the same; with enough materials and energy you can transform any environment. Terraforming Mars is then just a fair number of orders of magnitude larger prospect than anything done so far. Also to maintain the transformed turf of real estate it requires the continued application of energy and resources to maintain it.

In principle the terraforming of Mars is possible, but from a practical perspective that might be another thing. Also we may terraform just microscale regions of Mars, say under biodomes or some such thing. Before a planet wide terraforming is done, assuming it ever is, local terraforming under enclosures will happen first. Terraforming local regions on Mars would from our perspective now be an enormous endeavor. To convert a 1km^2 region into a habitable zone on Mars is likely outside the capacity of our economy. A piloted mission to Mars would likely cost in the upper 100 billion to the trillion dollar range. Building this terraformed biodome or zone on Mars would probably be two orders of magnitude more expensive and resource/energy intensive. We may never be able to work up the economic and energy cost for doing these things.

In some ways all these things are all cosmetic, and it requires constant effort of maintain them and more to grow them. We may convert a desert into a green territory, say by making it bloom with crops, or golf courses or artificial beaches (there is one not to far from where I live), and this temporarily changes the environment. However, if there is a system break down so the machinery stops running the desert reclaims itself. In the case of Mars it would be much the same.


Andrew Meronek November 20, 2012 at 6:24 AM

Don’t forget about genetic engineering to help humans adapt to the harsh environment. Any successful off-Earth colonization will likely have to involve both some level of terraforming and some level of genetic change.

Steve Kruckheimmer November 25, 2012 at 1:22 AM

Terraforming Mars is not a matter of “big engineering”, as with grooming a beach, or damming a river. That’s the misconception. Terraforming refers to literally changing the actual NATURE of the planet and atmosphere that surrounds it – to change the CHEMISTRY of these things. Grooming a beach is not terraforming – it was a beach before and after, it’s simply prettier! Some may have even preferred it in it’s natural state! You should avoid trivializing the objective of terraforming Mars by thinking it is simply a large scale landscaping project. Terraforming Mars means to literally change Mars into another Earth.

Steve Kruckheimmer November 19, 2012 at 9:40 PM

I’ve yet to hear an intelligent argument that we SHOULD “move” to Mars, or an argument that we COULD. These would be 2 entirely different arguments, and I’ve yet to hear them.

Steve Kruckheimmer November 25, 2012 at 12:37 AM

It’s amazing how much misinformation this article contains, or even that the article got published. For one, it’s NOT true that “Curiosity is taking the first ever radiation measurements from the surface of another planet in order to determine if future human explorers can live on Mars”. We alread know, and have for years, that there is a huge amount of radiation on the surface of Mars and that it is not safe for humans to live unprotected. Scientists are always measuring things, often things that have been already measured. Sometimes later measurements are more precise, or whatever. But it’s inexcusable to say that something is the “first ever” (with the atendant excitement and gee whiz hoo haw) when it simply isn’t. Will you writers at Universetoday get your act together. This article should have used the known dangerous levels of radiation as the premise for an article to explain why man can’t live on Mars because of this, instead it makes the opposite conclusion! Well, what do you expect from the uncritical, slap happy Mars advocates? I would expect any article on this particular subject to be on top of the latest data. Thanks for contributing to the “Averaging Down” project now underway regarding our global “collective intelligence”.

lcrowell November 21, 2012 at 3:00 PM

The experiments on Viking were based on what we expect biological organisms to do on Earth. In the end there were too many open ended problems to make firm conclusion. It could be that Viking detected life, but as we say in particle physics the sigma level is too low.

The Earth shakiing discovery by MSL could be the finding of organic compounds. That would be “Earth shaking” IMO.


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