To review current astrobiological knowledge and assess the prospects of life beyond Earth, the U.S. House Committee on Science, Space and Technology heard testimony Sept. 29 in Washington, D.C., from Cornell’s Jonathan Lunine and three other space experts on the reasons, ways and means for space exploration’s next steps.
“One of the most important outcomes of the last two decades of solar system exploration is the identification of four bodies in our solar system that appear capable of harboring life,” said Lunine, Cornell’s David C. Duncan Professor in the Physical Sciences and director of the Cornell Center for Astrophysics and Planetary Science.
Lunine spoke of the planet Mars, Jupiter’s moon Europa and Saturn’s moons Titan and Enceladus, providing general detail on how these vastly different bodies can add to human knowledge. “These bodies possess a certain set of characteristics that make them the best leads in the search for life beyond the Earth,” he said.
The representatives learned that Mars might have contained life and that Europa’s salty ocean may harbor organic (carbon-hydrogen) molecules.
For Saturn’s largest moon, Titan, Lunine explained, “Cassini and its lander Huygens have revealed methane clouds, rain, gullies, river valleys and methane-ethane seas. So we cannot resist asking whether some biochemical form of life might have arisen in this exotic, frigid environment. Titan is a test for the universality of life as an outcome of cosmic evolution.”
Lunine told Congress that the small Saturnian moon Enceladus has a large plume of material emanating from a series of fractures in its south polar region. “Enceladus has surprised us,” he said. “Make a list of the requirements for terrestrial-type life – liquid water, organics, minerals, energy, chemical gradients – and Cassini has found evidence for all of them in the plumes of Enceladus.”
Begging the big question, Lunine rhetorically asked, “So how do we find the sign’s of life in these bodies? The evidence will not be in entire living organisms. Much more likely is that we will detect signatures that indicate that life is at work – or was at work – in these environments.”
For each of the bodies, Lunine explained what the various exploratory missions would entail, explaining that the Mars 2020 rover will do “heavy lifting.” He told Congress that Europa’s mission – now in development – is crucial for any strategy in the search for life.
For a Titan mission, Lunine suggested dropping a capsule into one of the moon’s methane-ethane seas. A mission to Enceladus “provides us with the most straight-forward way to look for life,” he said, by flying through the plumes in the moon’s south polar region.
Other experts testifying were Ellen Stofan, NASA’s chief scientist; Jacob Bean, University of Chicago assistant professor of astronomy; and Andrew Siemion, director of the SETI Research Center at the University of California, Berkeley.