Ancient Earth, Alien Earths

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Panelists discuss how research on early Earth could help guide our search for habitable planets orbiting other stars. Photo Credit: (NASA/Aubrey Gemignani)

Panelists of at the event “Ancient Earth, Alien Earths,” from left to right:  Dr. Christopher House, Dr. Phoebe Cohen, Dr. David Grinspoon, Dr. Timothy Lyons, Dr. Dawn Sumner, Dr. Shawn Domagal-Goldman. Photo Credit: (NASA/Aubrey Gemignani)

At a recent event held at NASA headquarters, titled “Ancient Earth, Alien Earths,” a panel of scientists discussed how our knowledge of ancient Earth can help guide our search for habitable planets around other stars.

“We live in a revolutionary time in terms of our knowledge of the universe–this is the time of the exoplanet revolution,” began the planetary scientist and panel moderator David Grinspoon. “We’re also in a time of rapid discovery about the origin and early evolution of life on Earth.”

The event was held on August 20, 2014 as the public portion of a two-parts workshop sponsored by NASA, the National Science Foundation, and the Smithsonian Institution, focusing on the habitability of the early Earth.

Our Earth was very much an alien world in its early days. Its atmosphere started out oxygen-free. Methane levels were higher. And yet, our planet was able to support the emergence and evolution of life relatively early on. But what counts as a potential biosignature as we study these ancient times? And how can we apply that knowledge to our search for life elsewhere?

The panelists covered a wide range of topics–including the history of liquid water on Earth and on Mars; signs of microbial life in ancient rocks; the rise of oxygen in Earth’s atmosphere; and the evolution of animal complexity.

“The early Earth is our great natural lab,” said the biogeochemist Timothy Lyons.

But they also emphasized the need to keep thinking outside our Earth-centric box, and to remain open to the possibility of life elsewhere being drastically different than here on Earth.



The discussion participants included:

  • Phoebe Cohen, Professor of Geosciences Williams College, Williamstown, Massachusetts.
  • Shawn Domagal-Goldman, research space scientist, NASA’s Goddard Space Flight Center, Greenbelt, Maryland.
  • Christopher House, Professor of Geosciences, Pennsylvania State University, University Park, Pennsylvania.
  • Timothy Lyons, Professor of Biogeochemistry, UC Riverside, Riverside, California.
  • Dawn Sumner, Professor of Geology, UC Davis, Davis, California.
  • David Grinspoon, senior scientist, Planetary Science Institute, Tucson, Ariz. and former Blumberg NASA-Library of Congress Chair in Astrobiology, Washington