Profile | Chris McKay
Senior Scientist at NASA Ames Research Center
‘Drill Baby, Drill’
The question of whether life has ever existed on Mars has been at the center of a 50-year robotic exploration campaign that has seen an increasingly sophisticated armada of flyby missions, orbiters, landers and rovers dispatched to the red planet.
But while these probes have vastly expanded the body of scientific knowledge about Mars, the answer to that fundamental question about life remains as elusive as ever.
Christopher McKay, one of NASA’s most recognizable names in the field of astrobiology, argues that Mars probes to date have, quite literally, barely scratched the surface. The answers, he suggests, lie much deeper than the nuclear-powered Mars Curiosity rover has drilled to date.
Part of the problem, according to McKay, is that geologists are setting the Mars exploration agenda and that astrobiology is not a top priority. Having spent 30 years searching for signs of what he calls a second genesis — life originating from processes separate from what is known to have occurred on Earth — he now senses that the answer won’t come in his lifetime.
McKay, a co-investigator on payloads aboard the Huygens probe that descended into the atmosphere of Saturn’s moon Titan in 2005, the 2008 Mars Phoenix lander and Curiosity, which is still plying the martian surface, spoke recently with SpaceNews correspondent Leonard David.
Looking for life on Mars has been ongoing for decades and we’re still at it. Why such a long, drawn out search?
If we’re going to search for life, let’s search for life. I’ve been saying this to the point of exhaustion in the Mars community. The geologists win hands down as they are entrenched in the Mars program. The favorite trick is to form a committee to decide what to do. The people that are put on the committee, of course, are people who are funded to study rocks. So the committee recommends that we study rocks. They’ll say these rocks will give us the context of how to search for life on Mars. Then you say, well, that’s not right. But NASA Headquarters will say they asked the science community and they told us that this is what we ought to do. It’s kind of circular. The reason the committee told you that — it’s because you put a committee together of people who study rocks. It’s almost a Catch-22.
What’s the prognosis for obtaining a return sample from Mars?
I’ve said for many years that the sample return should be motivated by a combination of human exploration and science. The science community, I think, does itself a disservice by taking the attitude that there will be just one sample return ever in the history of the universe, so it has to be perfect. And a sample return mission that falls short of perfect shouldn’t be considered. I don’t understand where the logic is behind that. Let’s make a first sample return a quick and easy sample grab, demonstrate the key technologies. It builds enthusiasm for the idea of round-trips to Mars. It would also make getting a second sample return easier, both programmatically and technically. That argument falls on deaf ears when I try and bring it up in the community.
How does returning samples from Mars fit into human exploration?
The first thing is getting a mission that scoops up a bunch of loose dirt, puts it in a box and brings it back to Earth. If I was an astronaut, what I would be worried about is not the rocks. It’s the dirt. The discovery [by NASA’s Phoenix lander] of perchlorate in the dirt is cause to worry. It’s toxic, and the second cause to worry is the fact that it took us so much by surprise. There was no prediction or premonition that there would be perchlorate in the soil. The fact that it took us completely by surprise makes me wonder if there are other surprises in the soil. In fact, I would be surprised if there are no other surprises. Bringing back dirt is easy because it’s everywhere you land. You don’t need precision landing. You don’t need a rover. You land, grab some dirt and launch it back to Earth. The ground time on Mars could be one day.
Where should we go to look for signs of life on Mars?
Mars has been singularly disappointing on the surface. There are places on Mars that I recommend to drill to search for evidence of life. The first place is the Phoenix landing site — or that kind of place — the low northern plains on Mars where we know there is ice very close the surface. Drilling there down a meter you get to stuff that might have melted a few million years ago. The second site is a place that the Curiosity Mars rover has explored, but it didn’t get the attention that I think it deserved. Yellowknife Bay, at two drill sites, we drilled down 2 centimeters. We got through mud stone and we reached gray Mars — below the red covering on the surface. As far as we can tell, this is sediment that piled up in the bottom of a lake 3.5 billion years ago. We need to get well below the surface so that we’re seeing stuff that’s shielded from radiation. Drilling down, say 5 meters. The third site on my list is the ancient highlands on Mars with very strong magnetic fields. Places that have magnetic fields are very, very old — older than anything else on Mars that we see, and they’ve been relatively undisturbed. I advocate going back to the Mars Polar Lander site. But this time, don’t crash like we did in 1999. You’d need to drill very deep in that terrain — like 100 meters. We’ll get a record of ancient Mars like we can’t get anywhere else. So it’s drill, baby drill.
Do any of those recommendations square with NASA’s Mars strategy?
Right now, as far as I’m concerned, there is no alignment between the Mars strategy and astrobiology. What we have learned from studying Mars is that astrobiology has to go underground. You’ve got to start drilling. Curiosity has a drill and it had problems and we are now very cautious about using it. We’ve got to get back on that horse and send a bigger drill.
Would the headline “Life on Mars Discovered” change the future of Mars exploration and if so, how?
Yes, especially if there was an indication that that life was a second genesis. It would put exploration on hold while we figured out what the impact has been of the contamination we have brought to Mars. The Curiosity rover mission carried more than 278,000 microbes to Mars.
In your view, just how close are we to determining whether or not that Mars has ever supported life as we know it?
Not very close. To answer this question we need to go below the surface, more than a few meters. That technology looks pretty distant right now.
What’s the value of sending humans to Mars?
We have brains, we have eyes, we have feet and we have hands. Of all those capabilities, the one that’s proving the most difficult to extend to Mars remotely and robotically is the hand. What we need on Mars is hands. What’s needed are hands to operate a drill, pick up rocks — things you completely take for granted when you are a human scientist in the field.
What’s your view of the Mars One group that says it is selecting astronauts for one-way voyages to the planet?
I think that there’s a very small chance that Mars One will even make it to the launch pad, much less make it to Mars. But what they have illustrated is how deep and serious is the motivation in the public to go to Mars. Regular folks want to go to Mars in a serious way.
What about Elon Musk’s stated goal of colonizing Mars?
Musk is a very different scenario. He’s changing the game already in a very positive way. We’ve been trying to push them towards what’s called Red Dragon. It’s sending a capsule to Mars as a robotic science mission but deck it out with seats and maintain the interior habitat at conditions suitable for humans the whole trip. I have high hopes that Red Dragon will actually happen.
The science mission of Red Dragon would be what?
It could be sample return or it’s a deep drill payload. They could gain a lot of propaganda by landing a human-rated capsule on Mars — even though all it has in it is a drill.
How realistic is talk of terraforming Mars to make it more hospitable to humans?
There are things we know and things we don’t know. We know how to warm up planets — we have been doing it on Earth. Our research shows that we can use carbon and fluorine to make long-lasting super-greenhouse gases on Mars. Mars does have enough water, that we know, but we don’t know if Mars has enough carbon dioxide and nitrogen. Nitrogen is probably the most serious. The amount in the atmosphere as nitrogen is much too small. The presence of nitrate in the soil on Mars was recently confirmed. Calculations suggest it would take roughly 100 years or so to warm up Mars. Warm, wet and with a thick carbon dioxide atmosphere it would be suitable for life but not Earth 2.0. Humans would need an air supply — but not a spacesuit. Making the atmosphere oxygen rich is very hard. Our estimates suggest 100,000 years.
We’re more familiar with Mars than ever before. What has surprised you over the years and what in your view is the big message?
In a sense, in a funny way, the big messages about Mars have not changed for me since grad school. Mars is the only world that has any prospect of telling us anything about life beyond the Earth, although now we have two other candidates, Jupiter’s Europa and Saturn’s moon Enceladus. But Mars is the only place for humans to live and work beyond the Earth in any sort of meaningful, long-term way. Yes, Earth’s moon is closer, but it’s a place like Antarctica to set up a long-term base and visit. Mars has the prospect of people moving there and living there.
So there are two ultimate sources of motivation and interest in Mars. First, it is the connection to the search for life — perhaps finding a second genesis of life on Mars. Then it’s Mars as a potential place where humans can live and work.
I am happy to have contributed a small bit to those questions. I don’t imagine I will see answers to them anytime soon.