The Mission to Sample a Comet Going 84,000 Miles Per Hour—and Return
July 26, 2018 | Bloomberg
By Dimitra Kessenides
Steve Squyres was feeling restless. It was late fall 2013, and the semester was wrapping up at Cornell, where he’d been a professor for more than 25 years. As head of NASA’s Mars Exploration Rover mission, he’d just marked 10 years tracking Spirit and Opportunity, two six-wheeled robots that went to the red planet. They’d been designed to roam the surface for just 90 days, scratching and drilling into rocks and examining soil in search of evidence of water. Nearly a decade later, Opportunity was still rumbling along. Squyres wasn’t bored by its persistence, but there wasn’t much left for him to do.
He called Stephen Gorevan, a longtime friend and a co-founder of Honeybee Robotics Ltd., which specializes in drills and sampling tools for planets and smaller bodies. Squyres had included a Honeybee tool on the rovers, and he figured Gorevan might have something new and cool to show him. Squyres proposed a visit to the company’s New York headquarters.
Over the course of a day, Gorevan talked up a dozen or so projects. One in particular stood out: a nearly 18-foot-long pogo-stick-like retractable arm that Honeybee envisioned sending to a comet. The robotic “touch and go” system would grab a small chunk from the comet’s surface, about 100 grams’ worth, store it in a capsule, and return it unspoiled to Earth.
Squyres was captivated. Comets are icy bodies loaded with organic material—including carbon, hydrogen, nitrogen, and oxygen—that astronomers believe may have collided with Earth billions of years ago, starting the chain of events that led to the earliest forms of life and, eventually, to us. This primordial matter, which doesn’t exist anywhere else, remains frozen in comets, kept in a primitive condition since the birth of the solar system. “If you want to understand the emergence of life, comets get us closer than anything we can get our hands on,” says Squyres, a fit 62-year-old with short gray hair.
Of course, humans have never gotten near the dust and ice that make up comets. Driving back to Ithaca, N.Y., Squyres began working out how to rectify that. “A couple of neurons that hadn’t fired in well over a decade got me thinking,” he says. “I knew how important comet sample return was scientifically, and I knew that past attempts to propose it had failed.”
At the time, astronomers were waiting for images from the Rosetta mission, a probe launched to the comet 67P by the European Space Agency in 2004. Its photos were supposed to start beaming back to Earth in 2014. In theory, they’d give Squyres much of the data needed to design a mission to send Honeybee’s touch-and-go instrument there. So would Osiris-Rex, a NASA-sponsored asteroid study scheduled to launch in September 2016 that would also use touch-and-go technology.
Four and a half hours after leaving Honeybee, Squyres pulled into his driveway with an outline for his next big project. It would be expensive, but he knew NASA would be soliciting proposals in December 2016 for its periodic New Frontiers program, which sponsors space exploration missions with a budget of about $1 billion.
Squyres’s comet proposal—ultimately dubbed Caesar, for comet astrobiology exploration sample return—was selected late last year as one of two finalists. If it wins, it will give researchers their first chance to bring some of the organic stew from a comet’s surface back to Earth.
Date: 06/17/2016. Distance to 67P: 30.8km.
Comets are named either for the astronomers who identify them or with an alphanumeric code describing their orbit. 67P is also known as Churyumov-Gerasimenko, for the Ukrainian astronomers, Klim Ivanovich Churyumov and Svetlana Ivanovna Gerasimenko, who discovered it in 1969. With two misshapen lobes, the comet resembles a lumpy rubber duck spinning through space at 84,000 miles per hour. A day on 67P lasts a bit more than 12 hours; a revolution around the sun, nearly six and a half Earth years. It’s about 2.5 miles wide, with an orbit that goes beyond Jupiter at its farthest point from the sun. Thanks to Rosetta, we know more about 67P than any of the thousands of cosmic snowballs (as NASA sometimes calls comets) that have been identified.
Getting a spacecraft to a comet and collecting a sample is a complicated proposition. Irregularly shaped and small, comets spin quickly, and because of their size, they have almost no gravity. We know they’re frozen, and we know something of their chemical composition, but we understand almost nothing about their topography. A comet might be hard, like an ice cube, or it might be soft, like the slush pile at the base of a ski lift. “The environment of space is relatively easy if you don’t have to interact with a surface,” says Kris Zacny, a Honeybee engineer. “It can be anything, from very cohesive to very loose.”
Date: 01/17/2016. Distance to 67P: 84.3km.
Despite the challenges, NASA has made collecting such a sample a top priority. Comets are scientifically intriguing—the whole origins-of-life-itself thing—but some people think bringing celestial matter to Earth will someday be a big business as well. Commercial efforts, such as Deep Space Industries Inc. and Planetary Resources, an asteroid-mining startup backed by Google co-founder Larry Page and others, have promised investors enormous payoffs by accessing untapped resources in space. These efforts are widely seen as speculative—so speculative that, earlier this year, Planetary Resources had to lay off most of its employees after its funding dried up.
The challenge in space mining, according to Jim Keravala, the chief executive officer and a co-founder of OffWorld, a privately owned robotic mining and construction company in Pasadena, Calif., is that a scaling market doesn’t yet exist. OffWorld is developing machine learning technologies and modular robotics to be used in traditional mining, infrastructure repair, and construction. Eventually the technologies will be configured for use in space. “We’re treating Earth as our first celestial body,” Keravala says.
OffWorld supersedes another company he founded, Shackleton Energy, which sought to extract water ice from the moon. Shackleton wasn’t viable, he says, and ceased operations three years ago. “The future may be extraordinary, but there is a 20- to 50-year arc before you start, and your average space-mining entrepreneur is an enthusiastic zealot—I speak as part of that crowd.” OffWorld will draw on data from missions like Osiris-Rex and Caesar. “Until you can touch bodies in space extensively, you don’t have a business,” Keravala says.
In the near term, Honeybee is designing robotic drilling and mining equipment for research projects. Over 35 years, it’s grown from a few engineers working on New York’s Lower East Side to about 150 employees, with offices outside Denver and in Pasadena, across from NASA’s Jet Propulsion Laboratory. “Our niche is tiny, but someday it will have value when these commercial missions come together,” says Gorevan, who’s also Honeybee’s chairman. “We get most of our rare metals from China now. If we brought back one asteroid that was preexamined for having rare-earth metals, we’d never have to get anything from China again.”
Like many scientists, Squyres prefers not to think about commercial potential. He studied geology at Cornell but switched his focus after taking an astronomy class with Joseph Veverka, a member of the science team on NASA’s Viking mission, which sent two probes to Mars in the mid-1970s. “There weren’t many blank spots on the map,” Squyres says of studying Earth’s surface. “Geology is a compelling scientific discipline, but it didn’t have that ‘nobody’s ever been there’ appeal.” After taking Veverka’s class, he shifted to space.
Date: 03/19/2016. Distance to 67P: 12km.
As an undergrad, he studied images from the Viking mission, which showed, among other things, evidence of water on the planet—dried-up lakes and riverbeds. Shouldn’t mankind try to figure out what happened? Squyres went on to grad school, then took a job with NASA as a researcher at the agency’s Ames Research Center in Mountain View, Calif. Five years later he joined the faculty at Cornell alongside Veverka and Carl Sagan, the late renowned astronomer. Squyres maintained his NASA contacts and participated in missions whenever he could. “I spent 10 years writing unsuccessful proposals,” he says.
In the early 1990s, under then-Administrator Dan Goldin, NASA launched its Discovery Program, a lower-cost way to explore the solar system. The missions were competitive—“faster, better, cheaper” was Goldin’s mantra—and run by scientists or principal investigators. Mars got little attention, though, until the summer of 1996, when a paper in the journal Science raised the possibility that an Antarctic meteorite believed to have come from the red planet contained fossils. The findings suggested the existence at one time of living creatures on Mars, prompting President Bill Clinton to commit to exploring the planet. His announcement “cemented NASA’s commitment to search-for-life research and made it appealing in a whole new way,” says Laurie Leshin, president of the Worcester Polytechnic Institute and a co-investigator on Caesar.
Date: 08/18/2016. Distance to 67P: 6.1km
Spirit and Opportunity were launched in the summer of 2003, successfully touching down on Mars about seven months later. Spirit phoned home first, with Opportunity following three weeks later. The robots’ findings included craters suggesting Mars once had enormous lakes. They also captured spectacular images of dust devils and sandstorms and discovered minerals previously unknown to scientists.
Squyres had expected the rovers’ solar panels to eventually become so dust-laden that they’d shut down. Spirit last contacted mission control in March 2010, but it wasn’t dust that killed it—it had gotten lost after being stuck in a sand trap. Windstorms did blow the dust off Opportunity until late May of this year. Since then, one of the most severe Martian dust storms in decades has posed the greatest threat to the rover, and it’s gone silent. “Opportunity’s fate as a consequence of this storm will be either a miraculous recovery or an honorable death,” Squyres says, adding that there’s no telling when the weather will clear.
The budget for Caesar is about $1 billion, which, if the mission goes forward, would make it medium-size by NASA standards. It’s competing against Dragonfly, a mission led by Elizabeth Turtle, a planetary scientist at Johns Hopkins University, that would explore the chemistry and possible habitability of dozens of sites on one of Saturn’s moons.
The two teams are formulating their proposals, working out details. Honeybee has already started testing early designs of Caesar’s sampling system. At NASA’s Glenn Research Center in Cleveland, the instrument is dropped 500 feet into a giant vertical tunnel that’s essentially a vacuum. Aerated concrete, or aircrete, which has the density of light pumice, approximating that on 67P, is attached to the instrument, without touching it, so engineers can simulate sampling the material in zero gravity.
The next big milestone for the roughly 200 members of Caesar’s team will occur in 2019, when NASA will select the winning project. If theirs is chosen, they’ll spend about five years building and testing a spacecraft—Northrop Grumman Innovation Systems is designing one—and send it into orbit. It would take almost another five years for the craft to reach 67P. The launch is planned at the earliest for August 2024, with a tentative arrival date of March 2029. “Every mission is years in the making,” says Christopher Scolese, director of the Goddard Space Flight Center in Greenbelt, Md. Goddard is managing both Caesar and Osiris-Rex, with support from several partners, including Cornell University and the University of Arizona, where Osiris-Rex lead scientist Dante Lauretta is on the faculty. “It’s not like the movies,” Scolese says, “where it takes 90 minutes and a couple of nice words.”
Nor is it always heroic. For all the awesome tech that would make Caesar possible, Squyres talks a lot about meticulous preparation and “margin on top of margin on top of margin.” To him, risk reduction is almost a mantra and a way to meaningfully lower costs. In addition to drawing on the research from Rosetta and Osiris-Rex, Caesar would use solar electric propulsion to get to the comet, rather than chemical propulsion. This would allow the spacecraft to fly trajectories that wouldn’t otherwise be possible, Squyres says. “With chemical propulsion you do very short, intense burns that are followed by long periods of coasting. With solar electric propulsion you can do very long, gentle burns.” Those trajectories will reliably get Caesar to 67P and back. And since Rosetta has already studied 67P, Caesar’s spacecraft would carry few instruments, dramatically reducing its power needs and weight.
Squyres spent two weeks in 2012 in a lab submerged off the coast of Florida, as part of NASA’s Neemo 16 mission. The aquanauts were using the water’s low gravity to simulate field geology tests on asteroids.
Once the craft enters 67P’s orbit, in early 2029, the plan calls for six cameras to start snapping thousands of pictures that would help identify promising sampling spots. Site selection would begin almost immediately. The spacecraft would first get close enough to allow Honeybee’s touch-and-go arm to make trial contacts with the comet. Eventually, it would dig into the surface for several seconds to grab material. If the first attempt acquires enough—80 grams or so—then, Squyres says, “we’re out of there.” But the mission is designed to allow for two more touches; all told, the Caesar craft could spend as much as four years orbiting the comet.
The robot arm would seal off the sample, including any dust, ice, and gases, in a container and transfer it to a special capsule that looks like a roaming Roomba vacuum cleaner. Engineers at the Japan Aerospace Exploration Agency (JAXA) will build the capsule, a scaled-up version of a similar system used by the agency in the 2003 launch of Hayabusa, a robot that was sent to a small near-Earth asteroid and successfully returned with a sample for analysis.
“We had been thinking about making sample return missions a pillar of our space science mission program, but hadn’t thought about applying it to a foreign mission,” Masaki Fujimoto, a deputy science director at JAXA, writes in an email. But Squyres had done his research and had JAXA in mind. “The sample return capsule for Hayabusa was flawless,” he says, and aspects of that design would be perfect for Caesar, especially when it comes to keeping the sample cold.
If all goes well, its temperature would stay below freezing until the capsule lands at a rendezvous site in the Utah desert on Nov. 20, 2038. Then a team would pack the sample onto an ice truck and bring it to a facility in Houston, where scientists would begin analyzing it.
Squyres will be 82 in 2038. “I hope I’m still around,” he says. “I’m eating healthy foods, getting lots of exercise, taking care of myself. And my dad’s 91. So I’ve got good genes.”
He says it’s possible he won’t write a single scientific paper about results from the Caesar sample. He’s OK with that. “This may or may not succeed,” he says. “It could fail. It’s a huge gamble.” But he’s been preparing for this risk for most of his life, or at least since a moment in 1965, when he was 9 years old. His dad woke him one morning to observe a comet called Ikeya-Seki. Forecasters said it would be clearly visible to the naked eye, 10 times brighter than the full moon, despite being 80 million miles away. Ikeya-Seki didn’t disappoint, Squyres says. If everything goes right, 67P won’t either.