Venus is Earth’s closest neighbor and is similar in size and overall chemical composition. It sits on the edge of the habitable zone, the zone around a parent star where water could be present on a planet’s surface. However, Venus has gone down a very different evolutionary path from Earth, with a carbon dioxide-dominated greenhouse atmosphere resulting in surface temperatures of ~460°C (~860°F). Surface missions to Venus by the US and the Soviet Union and orbital missions by the USSR, NASA, the European Space Agency, and the Japanese have unveiled a very alien and complicated planet. The atmosphere super-rotates, and produces liquid sulfuric acid droplets that can corrode incoming science probes. The surface is dominated by volcanic landforms and is relatively geologically young. Some workers have interpreted the relatively uniform distribution of impact craters on the surface to indicate that a major volcanic resurfacing of the planet occurred about 750 million years ago, though other data contradicts this hypothesis.
Debate also is ongoing on whether or not Venus had a surface water ocean early in its history. Isotopic data from early probes indicates that the planet has lost an ocean’s worth of water over its history, but no clear signs of water remain on its relatively young surface. Data from future landers can help resolve the debate, as the signature of an early wet Venus should be present in the composition of surface rocks and more detailed isotopic studies of the atmosphere. This theory of an early, wet Venus has led some to suggest that life could have evolved on Venus and perhaps even persist in the stable cloud layers of the atmosphere.
As we search for Earth-like planets around other stars, continued exploration of Venus will help us to understand whether Venus was ever habitable, and thus further inform the likelihood of habitable planets beyond our solar system. Venus also serves as a laboratory for understanding CO2-dominated atmospheres and as a clear warning of the effects of continued anthropogenic carbon dioxide and methane emissions.
Ellen R. Stofan is the John and Adrienne Mars Director of the Smithsonian National Air and Space Museum, culminating more than 25 years’ experience in space-related organizations and a deep research background in planetary geology. Ellen also is Honorary Professor at University College London. Her research focuses on the geology of Venus, Mars, Saturn’s moon Titan, and Earth. Her favorite mission was Cassini, primarily because of her interest in Titan.
Before becoming NASM Director, Ellen served as NASA chief scientist and as the principal advisor to then Administrator Charles Bolden on NASA’s strategic planning and programs. She helped guide the development of a long-range plan to get humans to Mars, and worked on strategies for NASA to support commercial activity in low Earth orbit as it transitions from the International Space Station (ISS) to sending humans to the Moon and Mars in the mid-2020s. She supported NASA’s overall science programs in heliophysics, Earth science, planetary science, and astrophysics. And she worked with President Obama’s science advisor and the National Science and Technology Council on science policy.
Before stepping into the Chief Scientist role at NASA, Ellen was Vice President and Senior Scientist at Proxemy Research, a consulting firm specializing in planetary research, served as the Chief Scientist for the JPL’s chief scientist for the New Millennium Program at JPL, managing a team of about 100 scientists working on new technologies, and served as JPL deputy project scientist for the Magellan Mission to Venus, after doing postdoctoral there (while finishing her PhD).
Ellen has published extensively on her research and work and is co-author of the books Planetology: Unlocking the Secrets of the Solar System and Next Earth: What Our World Can Teach Us About Other Planets. She speaks frequently at technical conferences and to the public, and has addressed the World Economic Forum’s Council on the Future of Space Technologies at Davos, the World Science Festival, and SciFest Africa, to name just a few. Among her charitable activities, Ellen served on the board of the College of William & Mary Foundation for 10 years, serving as board chair and co-chair of the development committee as it planned a $1 billion fundraising campaign.
Among many awards and honors, she received the Presidential Early Career Award for Scientists and Engineers and the NASA Distinguished Service Medal, and she was named one of “CNN’s Extraordinary People of 2014.”
Ellen earned her BS at the College of William & Mary and her MS and PhD in geological sciences at Brown University.