Its like ordering a cocktail at a bar versus making one at home: At the bar, theres lots more booze to choose from and, therefore, a vast array of cocktails to be hadbut drinks cost a lot and the bar will eventually close. At home, you are limited to whatever few bottles you have on hand, but you can pour as much as you want, whenever you wantand you dont have to so much as put on pants to do it. Its going from a binge every few years to making a steady habit of it, scientifically speaking.
Instead of relying on multimillion-dollar missions, the ability to get a sample in front of any instrument you can think of will depend solely on the willingness of a NASA courier to make a hand delivery. Well, that and your ability to convince NASA that the samples will be used for something more worthwhile than biological compatibility tests involving making very expensive cocktails with Mars dirt.
This change has intriguing implications. Among other things, it means that the space mission wont really begin until all the space hardware has flown and safely returned samples to Earth, about six or so years after the mission first lifts off in 2026. MSR wont truly end until whatever year scientists exhaust the final soil sample, and that could take decades. Some of the best lunar science is being done today by examining samples of the Moon collected 50 years ago by Apollo astronauts.
For all the firsts that MSRs engineering mission will achieve in space, the true mission, the scientific mission, wont begin until all the space travel is over. Thats what makes it so hard, Zurbuchen says. The delayed gratification version of a mission.
Still, there needs to be something else extraordinarily compelling that is worth MSRs multibillion-dollar shipping charges. And there is: The mission is going to alter the meaning of the term life on Earth.
Theres a paradox about life in space. On the one hand, we know that space is utterly hostile to life. Theres lots of life on Earth, but the highest we have ever found an animal was in 1973 when a Rüppells griffon vulture (unsuccessfully) played chicken with a commercial airliner about seven miles up in the air. (The vulture lost.) Thats only about a tenth of the way to space; beyond that, we have found no complex life at all.
On the other hand, theres something of a consensus that theres probably life somewhere elseafter all, space is rather large. There are many times more stars in the universe than there are grains of sand on Earth: one estimate puts it at something like 60,000,000,000,000,000,000,000 (60 sextillion) stars, give or take a factor of 100. On average, each of them has several planets, and doing the math, thats a whole lot of chances for life to arise somewhere else.
Life as we know it is limited to a minuscule biological range, topping out seven miles up. On the other hand, we guess that this seven-mile limit doesnt represent the limit on all life everywhere. These two extremes present a question: When we talk about life, are we talking about a lot of life scattered across the universe, or just the rare, tiny, tragically isolated dot here and there? When we look at the night sky, are we looking at nothing but pure death, or thousands and thousands of different biomes?
We have no idea. But we do know a few things about life itself and the solar system in which we live. For instance, living creatures need some sort of solvent that enables them to metabolize food.
Life has to have the right conditions, energy, and time, says NASA Chief Scientist Jim Green. You take in a liquid, you eat fooddigestion requires liquid solvents to extract nutrients Then the liquid is used to eliminate the waste. Liquid is critical.
For everything on Earth, the liquid in question is water.
There is a band around every star that called the habitable (or Goldilocks) zonea region where you might find a planet that would be neither too hot nor too cold for liquid water to exist on the surface. Our suns habitable zone today includes Earth. Mars and Venus, our solar systems other terrestrial planets, are respectively at the very outer and inner edges of that zone. Mercury, the other rocky planet in the inner solar system, orbits far too close to the sun for liquid water to exist on its surface.
While the surfaces of Mars and Venus are each somewhere between very and monumentally hostile to life today, we have come to realize they werent always. Billions of years ago, for instance, Mars had a much thicker atmosphere that was better able to trap heat. This means that in the distant past, Earth wasnt the only planet with oceansMars and Venus had them too. So, part of what MSR is intended to do is search for evidence of ancient life on Mars.
We are looking for life not only in space, Green says, but in time.
Evidence from previous missions to Mars has accumulated, building toward the conclusion that the red planet may have previously hosted life. There are 4,700 minerals on Earth, but 300 of them can only be created by biological processes. Right now, with our mineralogy experiment on Curiosity, we’ve seen about 250 or 280 of those minerals, Green says.
Likewise, thermodynamics and statistics put a pretty strong upper limit on the size of molecules that will come together through happenstance and inorganic processes aloneabout 150 atomic mass units. Curiosity has found molecules twice that large, suggesting biological processes may have been at work. Mars past is still being explored, but MSR will probably provide the final proof that life once existed there.
Almost nobody believes that if you go to Mars and you dig a hole, something will come crawling out, Zurbuchen says. Todays Martian surface is still way too hostile for any organic life complex to skitter across the rocks. But it turns out theres an enormous grey area between the ability to support that complex life on the surface and the sheer, inhospitable lethality of deep space that physically separates Earth and Mars.
We know that life requires the right conditions, energy, and timeall of which were present on the ancient Martian surface. But what MSR will do, according to Zurbuchen almost no matter what, is tell us how easy it is to create life in an Earth-like environmenton a Goldilocks planet with liquid water on its surface, like ancient Mars or Venus. The big question now is whether life just crops up almost automatically on planets in their stars habitable zone, or if life really is a long shot, even when the conditions are right.
This result will come at an exciting time. The James Webb Space Telescope will start giving us our first data about exoplanet environments soon after its launch, slated for 2021. Among other things, the telescope may be able to make measurements of the atmospheres of exoplanets in the habitable zone of other stars, potentially revealing signs that there could be life on those worlds.
In 2025, NASA plans to launch the Europa Clipper mission to do flybys of Jupiters moon Europa. It has an icy surface covering vast salt-water oceans. The mission could find biological signatures indicating that life can arise even outside of a stars habitable zone. In 2026, the Dragonfly missiona robot quadcopterwill leave for Saturns moon Titan, which has oceans of liquid methane on its surface. Dragonfly could give us evidence that life can be based on a liquid other than water.
This quartet of missionsMSR, the James Webb Telescope, Europa Clipper, and Titan Dragonflyhave the potential to radically alter our notion of how common life is in the universe. By the mid-2030s, we may have evidence of a fundamentally different universeone dotted with liferather than the hostile, sterile one we know about today.
Weve learned in the last 30 years that rocks from Venus, Earth, and Mars may havevery infrequently in the distant pasttraveled from one world to another. Giant meteor impacts, like the one suspected of killing the dinosaurs 66 million years ago, can blow chunks of rock all over the solar system.
And weve also discovered that, as hostile as space is to humans, under the right conditions, a microbe living on one of those rocks might be able to survive the trip. This raises the possibility that the entire evolutionary tree of life on Earth may not be limited to just life on Earthbranches of that tree may come from other worlds. If, that is, there has ever been life on other worlds.
But we cant really get at any of our questions about Mars until we can touch a pristine sample of Martian soil with our own hands. And in doing that, we may discover that not only is there life out there in space, but that our life here comes from space as well.
G. Ryan Faith writes about and consults on space and space policy issues. He served as committee staff supporting the House Subcommittee on Space. Prior to that, he was Defense and National Security Editor at VICE News. You can follow him on Twitter at @Operation_Ryan or reach him by email at ryan@exocent-strategies.com.