Life on Mars

John Grotzinger talks about once-flowing rivers, the drinkable water—and when we’ll walk on the red planet

by Kate Lunau

The once-flowing rivers, the drinkable water—and when we’ll walk on the red planet

Roman Cho/Getty Images

On March 12, John Grotzinger and a team of NASA scientists made a stunning announcement: Mars once had the right conditions for life, with flowing surface water so benign we might drink it. This finding comes courtesy of the Curiosity rover, which drilled and analyzed a rock sample from an ancient stream bed at Gale Crater on Mars. It’s the first habitable environment we know of, other than on Earth. As the first primitive forms of life were emerging here, it now seems possible life might have been taking hold on Mars, too. John Grotzinger is chief scientist on Curiosity, which has been exploring the Martian surface since Aug. 5, 2012.

Q: Scientists have found evidence of water on Mars before. What about this new finding tells you life could have existed there?

A: We’re excited because we’re getting a peek at what we call “grey Mars,” instead of red Mars. [Curiosity’s drill cuttings were green-grey in colour, not red like the surface of Mars, which is highly oxidized.] We’re seeing not just the presence of water, but water with a chemical composition that looks friendly toward microbial life. This is the kind of water that, if you drank a glass, you wouldn’t keel over and curl up, although I’m not sure I would want to plumb it into an urban district. We also see a diversity of minerals, which vary in their oxidation state. We think of these minerals at Gale Crater as though they were little batteries [which can give energy to microbes].

Q: How much water are we talking about? Was it ankle-deep or hip-deep?

A: There would have been flowing rivers at one point. At the ends of these rivers, there may have been lakes. We don’t know how long the lake was around for; it could have dried up very quickly. But it looks like we found that place.

Q: How long ago was this?

A: Most of us think it’s certainly greater than three billion years. It could be 3.5 billion. This is the same time we see the very oldest records of life on Earth—[when] life may have been evolving on Earth.

Q: So what happened? Why did the habitable environment on Mars disappear?

A: It could be related to the termination of plate tectonics. On Earth, plate tectonics involves churning [of metals] within the mantle and core. When they circulate, it generates a magnetic field, and gives rise to something we call the magnetosphere, which has electrical charges that deflect the cosmic and solar wind that comes to Earth. We already know that, if you stay out in the sun too long, that’s bad for you. If you were on the surface of Mars today, you would not last very long—because of all the harmful cosmic and solar radiation. And so the thought is, maybe Mars lost that protective envelope, and with it, Mars may have lost atmosphere. Mars has a much lower gravity, about one-third of Earth’s. The thought is that the very light gases—things like hydrogen and oxygen—got stripped away into space. The atmosphere on Mars today is much, much thinner than Earth’s: it’s about one-thousandth of Earth’s, but we think there’s a chance that at one time, it may have been as thick as Earth’s. It was apocalyptic climate change on Mars that changed it.

Q: Astronomers now say there are probably hundreds of billions of planets in our galaxy alone. If we know that habitable environments can exist off Earth—even right next door—what does that tell us about the chance there’s life elsewhere in the galaxy?

A: When you can confirm an ancient aqueous environment to be this benign, on a planet that’s as foreign as Mars, you’re left to wonder. These are both terrestrial planets; they both have the same prebiotic chemistry available. It seems like the odds of prebiotic reactions happening that did create life could have more readily happened on Mars than we ever would have guessed.

Q: Based on this, do you think there could be life on Mars today? Is there still water at the surface, or under the surface?

A: We’re not equipped to do a life-detection mission. But there are orbiter missions that have such high-resolution cameras that they’re able to see places that we call “slope streaks.” It looks like, on the sunlit side of some hill slopes, there might be places where water could be emerging today. I think most people would agree the current surface environment of Mars is very inhospitable. But if life once originated on Mars, and then the climate changed so dramatically, maybe these microorganisms took refuge in the subsurface. What we are describing is the kind of environment where very primitive microbes could have lived, whose only energy source is really the rocks themselves: they literally eat rocks. They don’t need sunlight, and they don’t need to be on the surface. They could exist in the subsurface. I think there’s a lot of interest on the part of NASA to try to explore those kinds of environments one day.

Q: On Earth, we’ve found microbes that can thrive in pretty much any environment imaginable, including deep underground.

A: Yeah. Absolutely. In the last 20 years of modern microbiology, we’ve learned about microbes that grow in extreme environments, and we call them extremophiles. They can live in very low pH; very high pH; very hot water, including boiling water. In the deep mines in Canada, in Timmins [Ont.], people have gone down and discovered that miles deep in the Earth, you find microbial communities. That’s the kind of environment we’re trying to describe with Curiosity.

Q: How much of a challenge was it for your team to analyze this rock sample? It was the first time a robot sent from Earth actually drilled on another planet.

A: It was a lot of work. There are so many things you have to check to make sure the rover is functioning, and that all the systems are operating, and that the arm is working and the turret at the end of the arm that holds the drill is working, and that it’s all precisely placed. Then you look for a rock that you think will be scientifically interesting, but that when you drill it, it won’t just turn into quicksand or something. We had to worry about all of these details, and then we had the hand-wringing after drilling the rock. We had to wait a couple of sols [Martian days] until we could get visual confirmation that we had processed a sample. We put maybe a baby Aspirin–size sample into the instruments. It just turns out we hit pay dirt.

Q: Now that NASA has a plutonium-powered, car-sized rover driving around on Mars, how soon will you be able to put some human astronauts there?

A: The key technology for getting humans to Mars is being able to bring them home. It’s a longer trip than the moon, but more importantly, Mars has real gravity. So you have to develop a vehicle that will lift something off the surface. The plan is to first do a Mars sample return: to build another rover, drive it around, collect samples and then bring them back. This would be a set of missions, and [it would] take probably a couple of decades. It’s in the planning stages now.

[We would start by building] basically the same kind of rover as Curiosity, which would not just drill, but collect sample cores, roughly the size of pens or pencils. It would then cache those cores for return to Earth. The cache would be something that looks like a bowling ball. The next decade, we would send a retrieval vehicle that would go pick up the bowling ball and put it into orbit around Mars. And then, a couple years after that, you’d send a retrieval vehicle that would go get the bowling ball and return it to Earth. Those three steps are what should pave the way for human exploration of Mars.

Q: If we brought a core sample from Mars back to Earth, I’d imagine scientists could do much more with it than Curiosity can manage, even with its high-tech tool kit.

A: As soon as you get a sample back to Earth, you’ve got instruments that work at such high levels of accuracy. There would be other elements and minerals you could measure. We’re beginning to get a whiff of organics with Curiosity, but we’re never quite sure: is it contamination we brought with us? The amount we’re seeing is small enough that we have to be very careful with what we say. Whereas, if you bring a sample back to Earth, you could work with tiny amounts to find out whether there is organic matter there, and if it has anything to do with biology.

Q: Organics are a key ingredient to life. If Curiosity makes a confirmed find of organic compounds on Mars, what will that mean?

A: The solar system is full of organics. We just had an announcement of organics on the dark side of Mercury. [The organics they found were similar to tar and coal, and are believed to be delivered by comets and asteroids.] Meteorites come into Earth full of organics. So, if Curiosity finds organics and they aren’t contamination we brought from Earth, then they either came from Mars or somewhere else in the solar system. If we determine they came from Mars, we have to figure out whether they were manufactured by a biological process, or not.

Q: What’s next for Curiosity?

A: Finishing up what we’re doing here. Trying our hand at looking for organics. Then we’re off to Mount Sharp [a 5.5-km-tall mountain of sedimentary rock] to decipher the record of planetary history and detect more, and different kinds, of habitable environments.




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Life on Mars

  1. Red rover: Red rover:
    Let the earthlings come over.

  2. “The atmosphere on Mars today is much, much thinner than Earth’s: it’s about one-thousandth of Earth’s”

    wrong!

    the pressure (636Pa) is 159 times less

    the mass (0,020kg/m3) is 61 times less

    • he could be talking about the number of molexules, not the pressure they exert. Based on what he said, it is mostly heavier molecules that are in the atmosphere, thus there are less of them and they exert a higher pressure at the surface than our air.

  3. I think their funding depends on finding a reason to continue exploration of these barren planets , hence the exaggerated claims of water and organic matter ..

    • Do you have anything to back that up? Or are you just being a miserable sod?

      • “miserable sod” is how you might describe the soil on Mars , perhaps ?

        • No.

  4. He’s just spouting the NASA and “planetary science community” (which means the Archbishops of the Holy Academy) party line on human missions -which is currently about a totally ludicrous, extremely over-complicated multi-decade plan that everyone knows is wasteful and will not happen. Non of this long-term vague programs do. Robotic sample return has some justification as a part of a robot EDL test of the human mission systems, but that’s it, and not more than once. The scientists on the mission will be able to analyze in a real lab right on Mars, and WAY more than a bowling ball sized amount of samples can be returned.

    Curiosity has confirmed what the previous robots indicated and many theorized all along: Mars was habitable, and for some time.

    Now, we can certainly dicker about for decades with more robots, and in many areas, they have a contribution to make. But this needs too be understood: the chances of any conceivable robot mission finding subsurface life or surface fossils are very, VERY small. Only a smart human mission, such as Mars Direct, or the Design Reference Mission that NASA has had and been updating for 18 years, has any real chance, on any time table, of conducting the kind of search we need on Mars now.

    Curiosity, Opportunity, and Spirit, have cost about $3.5 billion so far, the next rover is “expected” to cost about $1.5 b, and at least $5 b more for sample return. At that point, we will know what we know now plus what else Curiosity finds out about its little area, what the next Curiosity-class rover finds in its little area, and we will have a few dozen little near-surface core samples of rock to analyze in labs here on Earth. 2 or even 3 decades, and $10 billion -at the absolute very least, really it will surely be more- for a pittance of the data out there. And we will STILL have to suck it up and send people to get the data we want.

    OR the Congress could offer a Mars Prize -$20 b, $15 b, even $10 b- to the first organization to conduct a human science expedition to the surface of Mars and back to Earth. Certain tasks would have to be done, certain standards would have to be followed, but beyond that, it would be up to the bold explorers how they would get it done. In the private space world, there might even be a substantial profit for the group at just a $10 billion or less Prize.

    Would you rather have our money go to truly exploring Mars and making the next giant leap in the history of humankind, or to keeping JPL in business for the next 20 years?

    • Mars Direct eh?

      Yaaay Robert Zubrin

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