One Friday this fall, a sleepy home on a tree-lined street blocks from the Penn State University Park campus became mission control.
In a small office just off his family’s living room, Christopher House studied a rust-red landscape on a large computer screen, conferred with colleagues from around the world on his laptop via video chat and helped plan a string of commands that would travel even farther.
The instructions raced some forty million miles away —straight to the surface of Mars and to the $2.5 billion marvel of engineering and science waiting for its daily agenda.
House, a professor of geosciences, is a science theme lead on the NASA Mars Curiosity rover mission, led by the Jet Propulsion Laboratory in Southern California. Several times a month, he leads the team charged with planning the rover’s science tasks for the following Martian day.
“Each time we drive, we wake up to an entirely new field of view with new rocks and new scientific questions to ask,” House said. “When we review these photos during our planning session, it’s sort of a whole new world each time.”
Launched in 2011, the NASA mission to explore Mars’ Gale crater is among a fury of space exploration activity in the past decade. Probes are exploring the Moon, Mercury, Venus, Mars, asteroids and comets, and the outer solar system. NASA alone spends more than $1 billion annually on planetary science, and companies like SpaceX and Blue Origin are pioneering commercial space flight.
These missions increasingly turn to scientists like House, who has long studied ancient Earth and the conditions that gave rise to life on our planet, to apply their expertise to other worlds.
It’s an exciting time to be a geoscientist.
“This is the golden age of planetary science,” House said. “I hope that universally everybody can appreciate how phenomenal it is that we send these sophisticated robots across the solar system.”
To boldly go …
If planetary science is experiencing a golden age, Penn State is doing its part to rise to the occasion.
The University launched the Consortium for Planetary and Exoplanetary Sciences and Technology this fall to focus efforts on studying how planets form, evolve, and become habitable, and on detecting and potentially exploring these worlds.
Leading experts in geosciences, meteorology and atmospheric science, materials science and engineering, astronomy, and engineering will collaborate to lead space missions and develop equipment used on those projects.
“Penn State already has many of the pieces in place to establish a world-class planetary science program,” said James Kasting, Evan Pugh University Professor of Geosciences and inaugural director of the consortium. “The consortium offers a unique opportunity to coordinate our efforts and to become a leader in the emerging field of planetary system science. Together, we can address some of the most fundamental questions asked by humans.”
Penn State geoscientists study everything from how life thrives in some of the most extreme places on Earth, like thermal vents at the bottom of the oceans, to the locations of “goldilocks zones” in the cosmos where we may find we are not alone.
Kasting played an important role in developing the concept of these habitable zones, or areas around stars that may have conditions ideal to support liquid water and perhaps life. For him, the search for life in our solar system and around distant stars is the ultimate goal.
“Even if we search the cosmos and come up with a negative result, if we see a bunch of Earth-like planets and none of them have life, we’ll know we hold a very special place in the universe,” Kasting said. “But I was a fan of Carl Sagan growing up, and Sagan was much more optimistic than that. And I’m more optimistic also.”
Life on Mars?
On its year-long trip up and then back down Mars’ Vera Rubin Ridge, the Curiosity rover made an unplanned pit stop.
House and his colleagues noticed something strange in the latest images. On an ancient lakebed dominated by mudstone, they saw small, black, stick-like features dotting the landscape. A one-day stop turned into a week.
Curiosity snapped photos and tested samples with its onboard laboratory. The data showed the sticks were ancient iron deposits that told a complex story of liquid that lasted many millions of years on the red planet.
“That’s really important because it illustrates the geological cycles and the hydrogeological cycles on Mars were persistent,” House said. “This was not a story about how Mars had water one time and then didn’t. Like Earth, it was a long-term, multiple-step cycle.”
Scientists pieced together the story: the lakebed lasted perhaps ten million years before being buried and turned to rock, and then later flowing water leached iron from the rock, mobilized it and redeposited as the black sticks.
“What we’re really learning is there was a complex history on Mars that involved water at every step,” House said. “And the diverse chemistry in those fluids points to a habitable world some 3.5 billion years ago.”
Future missions will be tasked with finding direct evidence of past microbial life.
Mars 2020 Perseverance Rover, which launched in July, can collect and store samples that a future mission may return to Earth. Elsewhere, space missions are working to bring samples of asteroids back to laboratories around the world.
Back on Earth, scientists like Katherine Freeman are studying isotopes, or different forms of atoms, in small organic compounds to better understand whether they carry signatures of biotic or abiotic processes.
“I’m an organic geochemist who has spent my career studying organic molecules preserved in sediments and rocks on Earth, and suddenly there is a whole new world of organic chemistry to potentially explore,” said Freeman, Evan Pugh University Professor of Geosciences. “It’s truly an exciting time.”
Freeman serves as director of the NASA-funded Astrobiology Center for Isotopologue Research at Penn State, a new international collaboration that uses cutting-edge observational and computational tools to study these isotopic fingerprints.
Her lab is working to increase the sensitivity of the instruments so they can extract information fro the trace amounts of elements found in Martian soil samples.
“There’s not a lot of organic carbon on Mars— it’s pretty red for a reason,” Freeman said. “The things future missions bring back will be very low in concentration, so we need to be ready to make measurements on very trace amounts of carbon to help us understand its origins.”
The pale blue dot
Step into the cool, damp cave where slime grows on the walls in the darkness and where sulfur is on the menu, and you may not recognize Earth.
“Conditions underground are more similar to a planet that we’re only getting to know now, which is the early Earth,” said Jennifer Macalady, an associate professor of geosciences. “I really think about it as a different planet entirely, because it’s evolved so far away from its initial state.”
Macalady is an explorer. She steps into some of the most extreme environments on Earth, like caves that contain some of the planet’s most unusual lifeforms.
“What’s special is you can go in there and manipulate things without a robotic arm, or a submersible or a spaceship,” she said. “Yet it’s still like being on another planet.”
In an Italian cave affectionately known as the “slime palace,” colonies of microbes—some that look like goo and others that resemble soil— cover the walls, thriving away from sunlight and photosynthesis.
The organisms can help scientists better understand life on early Earth, as those organisms had not yet learned to harvest photons through photosynthesis. Humble microbes dominated much of history of life on Earth, and so these tiny organisms are what we might expect to find on other worlds.
“I tell my students; Earth was microscopic life for eight-ninths of its history,” Macalady said. “It’s just the last blip that you can even see something with your naked eye. And if we don’t understand what early Earth was like, how will we know where to look elsewhere?”