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Saturday, May 18, 2024

NASA’s Epic Gamble to Get Martian Dirt Back to Earth

There are two kinds of places in the universe, as far as we know. The part here, on Earth, with all the life. And the rest of the universe: endless, sterile nonlife out to the ends of infinite creation. But right now, there is a mission in the works to bring back dirt from Mars and see if life really is alien to the rest of the universe.

It’s called the Mars Sample Return mission. During the next 12 years or so, NASA and the European Space Agency will team up to send a rover to the red planet, where it will collect a variety of soil samples. Another rover will then gather the samples, and the samples will be put in a rocket and launched from Mars. The rocket carrying samples will rendezvous with an orbiting spacecraft that will come back to Earth, bringing the soil samples with it.

The Earthlings in charge of this enterprise are, to put it mildly, almost giddy at the thought of getting their hands on Martian regolith. “A single sample… will change how we think about everything,” says Thomas Zurbuchen, NASA’s associate administrator for science. “It will be the most valuable thing on Earth.”

Mars Sample Return—MSR in NASA’s inevitable initialism—will mark the first time that humans make a round trip to Mars, and it will be the first physical, tangible, two-way cause-and-effect connection between Earth and another planet. For the first time in recorded history, we’ll be able to physically touch and interact with a pristine piece of another planet.

First, however, we have to get MSR to Mars and get some dirt. The details are devilish, indeed.

Outer space is no more than 60 miles straight up—a bit more than the width of Rhode Island, a bit less than the width of New Hampshire—but energetically, it’s very far away indeed. To get into the lowest of low-energy orbits, you need to accelerate to more than 17,000 mph, which requires rocket engines that convert fuel into kinetic energy at obscene rates.

And those burn rates must be controlled precisely; if you convert your rocket fuel’s chemical energy into kinetic energy too quickly, you exceed the material limits of the engines. This immediately results in an aptly named RUDE—Rapid Unplanned Disassembly Event, also known as a catastrophic explosion. If you convert that fuel into speed too slowly, you make an unexpectedly quick return to Earth, culminating in severe impact braking and an immediate RUDE.


We could build a rocket so sturdy that it’d never explode, but no realistic amount of energy (short of a string of nuclear explosions) would be able to lift the thing into orbit. And anything light enough to get easily into orbit would be so flimsy it wouldn’t survive the trip. If the Earth were 50 percent bigger in diameter, no amount of engineering in the universe would get a rocket all the way to orbit; there would simply be too much gravity for any design or any chemical propellant to overcome. As it is, even the most advanced rocket still tests the outer limits of 21st century materials and design.

And that’s just getting to orbit—getting to Mars is a whole other ballgame. The International Space Station orbits at about 250 miles above the Earth; the Moon is 1,000 times farther away than that. Mars, meanwhile, is 1,000 times farther away than the Moon.

Think of it this way: If the distance from Earth to the very beginning of space were the length of a baseball bat, the distance from Earth to the ISS would be about the length of a four-door car. One-thousand times greater than that is about 2.5 miles, or about a 10-minute bike ride. One-thousand times that is 2,500 miles, or the distance from New York to San Francisco.

Because the vast distance is only one of the many obstacles that complicate a trip to Mars, the odds of actually getting something there in working condition aren’t anything you’d accept when booking your next flight to Rhode Island or New Hampshire. Since the first attempt in 1960, only 19 of 45 missions to Mars—just over 40 percent—have been complete successes.

Even after more than a half-century of experience and technological development, every mission to land on Mars is still a one-of-a-kind gamble. Today, with all our knowledge, this complexity and difficulty mean it costs around $1.5 million in shipping and handling for every pound of robotics and instrumentation you want to send to the Martian surface.

That is why it is so heroically challenging to touch and do things on another world. As of right now, there is no such thing as “just sending stuff to Mars.” That may change someday, but today it takes billions of dollars, thousands of engineers and scientists, and decades of experience to so much as dig a hole on Mars, a task anyone on Earth can do with five minutes and a five-pound shovel (which would run you a cool $7.5 million just to ship to the red planet). Mars is our astronomical next-door neighbor—it’s about as easy a trip as we can take—but our ability to interact with it is just barely this side of nonexistent.

Passive observation, looking up in the sky, has been the only option for interacting with Mars for almost all of human history. Over the last 400 years, we’ve been eyeballing the planet with increasingly powerful telescopes, but there are limits to what you can learn about a place with passive observation alone. (You would need a telescope with a primary mirror bigger than South Carolina to look at individual pebbles on Mars.) So, starting in 1965, we sent cameras out to Mars orbit, then had them snap photos and transmit them back.

But if you’re willing to go the all the way down the Martian gravity well and touch down on the surface with a lander or rover, the range of scientific possibilities explodes. Humans did this successfully for the first time in 1976, with the Viking missions. Landers and rovers can physically interact with their environment and do exciting new things like flip a rock over to see what’s on the other side, scrape away the top surface of a rock to see what it looks like inside, or drill holes into the ground. Scientists can then deploy instruments, like the X-ray diffraction instrument on the Curiosity rover (used to observe crystalline structure in rocks), that need to be right next to a target to work.

The tricky part here is that science continually generates bigger and more complex questions; solve one riddle, and you end up with two new ones. Anyone who has found themselves intellectually run aground by a 4-year-old repeatedly asking “Why?” has experienced this phenomenon firsthand. Over time, answering those questions requires ever-increasing scientific firepower.

Even on Earth, hunting for signs of life from billions of years ago isn’t easy and requires both field investigation and detailed analysis in the laboratory. There’s only so much you can do at the scene of the investigation; eventually, you need to send samples back to the lab for further analysis. We are now getting to the point where we’re asking the kinds of questions about Mars that we can’t answer with fieldwork alone.

Broadly speaking, scientists want to bring back Mars samples to address three different sets of questions: geological, biological, and technological. Geologists want to understand, in detail, the history of Mars and see what conditions have prevailed there over the last few billion years. Biologists want to figure out if those conditions gave rise to life. The technologists want samples so they can figure out the details, feasibility, and risks of sending humans there someday.

As challenging as a round trip to Mars is, it makes more sense as a way to answer today’s scientific questions than sending the lab equipment to Mars. For example, geologists would love to send an ion microprobe that can measure elemental abundances at the scale of millionths of a meter; the abundances of particular isotopes can then be used to determine the age of a specific bit of rock in a sample. But those machines are big and power-hungry. Shrinking one down to size and getting it to Mars would be a costly engineering project you’d need to manage before even looking at your first Mars sample. But even if you manage to make it lean and portable, room for science payloads is zero-sum. Adding an ion microprobe means taking off something else.

Further, anything you can send is sharply limited in capability. The enormous cost of shipping instruments not only restricts what you can send to Mars, but it also puts a considerable squeeze on their power and mass, bounding their precision and capabilities.

The limitations on precision and delicacy go beyond the instruments to the handling of the samples themselves.

The immense distance to Mars means the fastest the speed of light will let you send a signal to Earth to Mars and back again is just over six minutes round trip (in the worst-case scenario, that roundtrip time for a signal climbs to almost 45 minutes). That means there’s an enormous lag between telling your robot to do something, seeing if it worked, and then telling it to go the next step. The time needed to do something, observe the results, decide what to do, and then act is critical. Doing anything with up to a 40-minute lag is an exercise in patience and a recipe for missed opportunities.

Compare this with human reaction times of about a quarter second. In an eight-hour shift, a person on Earth is limited—at absolute theoretical maximum—to about 78 round trip communications with something on the surface of Mars. If you bring that sample back to Earth, the time needed to send a signal back and forth to an instrument drops to nearly zero. A scientist in the lab could (in theory) complete tens of thousands of interactions with a sample in the same eight hours. Once you can handle and interact with a sample continuously, it allows you to do all kinds of new science, like looking for extraordinarily small things like fossils of ancient microbes, imprints of mold spores, and trails left by stone-eating bacteria. In the lab, investigators can pick apart rocks with incredible care and precision.

Scientists have been thinking for decades about the kinds of experiments they could do once they have samples back on Earth. Indeed, the most recent report, “The Potential Science and Engineering Value of Samples Delivered to Earth by Mars Sample Return,” says “Potential [signs of life on Mars] can be investigated thoroughly only by observation-guided sample preparation, followed by investigations by laboratory consortia that apply state-of-the-art techniques.”

The change in both how samples can be processed, and the tools used to examine them will be huge. Let’s just take one example out of hundreds or thousands. In theory, it might not only be possible to find impressions left by hypothetical Martian mold spores in ancient rocks but also to immediately test the sedimentary rock to determine how long ago those spores landed in Mars mud. And all that could be done in the space of days or weeks.

The ability to do all that “observation-guided sample preparation followed by investigations” would be such a huge breakthrough that the scientific value of going even from zero Martian soil to a little Martian soil is effectively immeasurable. Not so the price tag; MSR will cost at least $7 billion.

This graduation from sending information back to Earth to sending actual Martian stuff back to Earth involves fundamental changes in the way we think about space exploration. Up to now, we’ve been able to go to Mars and choose among a whole world of different samples—but we could only do so much with them. With MSR, it’ll be the opposite.

It’s like ordering a cocktail at a bar versus making one at home: At the bar, there’s lots more booze to choose from and, therefore, a vast array of cocktails to be had—but 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 want—and you don’t have to so much as put on pants to do it. It’s 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 won’t 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 won’t 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 MSR’s engineering mission will achieve in space, the true mission, the scientific mission, won’t begin until all the space travel is over. “That’s 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 MSR’s multibillion-dollar shipping charges. And there is: The mission is going to alter the meaning of the term “life on Earth.”

There’s a paradox about life in space. On the one hand, we know that space is utterly hostile to life. There’s lots of life on Earth, but the highest we have ever found an animal was in 1973 when a Rüppell’s griffon vulture (unsuccessfully) played chicken with a commercial airliner about seven miles up in the air. (The vulture lost.) That’s only about a tenth of the way to space; beyond that, we have found no complex life at all.

On the other hand, there’s something of a consensus that there’s probably life somewhere else—after 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, that’s… 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 doesn’t 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 food”—digestion 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) zone—a 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 sun’s habitable zone today includes Earth. Mars and Venus, our solar system’s 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 weren’t 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 wasn’t the only planet with oceans—Mars 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 alone—about 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. Today’s Martian surface is still way too hostile for any organic life complex to skitter across the rocks. But it turns out there’s 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 time—all 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 environment”—on 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 star’s 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 Jupiter’s 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 star’s habitable zone. In 2026, the Dragonfly mission—a robot quadcopter—will leave for Saturn’s 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 missions—MSR, the James Webb Telescope, Europa Clipper, and Titan Dragonfly—have 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 universe—one dotted with life—rather than the hostile, sterile one we know about today.

We’ve learned in the last 30 years that rocks from Venus, Earth, and Mars may have—very infrequently in the distant past—traveled 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 we’ve 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 Earth—branches of that tree may come from other worlds. If, that is, there has ever been life on other worlds.

But we can’t 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.

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