In March 2018, if all goes as planned, a SpaceX Falcon 9 rocket will send an instrument designed and fabricated at MIT, the Transiting Exoplanet Survey Satellite (TESS), into high Earth orbit. From an altitude of about 400,000 kilometers, TESS will conduct an all-sky survey that brings a new perspective to the search for planets beyond our solar system.

On the fourth floor of MIT’s Building 37, a dozen computers working in parallel will process data relayed from the orbital satellite, and about 30 MIT scientists and engineers will pore over it for clues about our astronomical neighborhood. “MIT has the overall technical and science responsibility for the mission,” says TESS principal investigator George Ricker ’66, PhD ’71, a senior research scientist at the MIT Kavli Institute for Astrophysics and Space Research. Fellow Kavli scientist Roland Vanderspek PhD ’86 serves as deputy PI. Altogether about 300 researchers from more than a dozen universities and other institutes are taking part in this NASA Explorer mission. TESS’s unique capabilities should enable it to pick out small, relatively nearby planets (within a few hundred light-years of Earth) that offer at least some of the conditions deemed necessary for life. The ambitious endeavor could give humanity its best shot yet at understanding just how unusual our planet is, or isn’t, in the grand scheme of things.

To fulfill its scientific objectives, TESS will rely on the “transit method,” looking for periodic dips in a star’s brightness that could be caused by an orbiting planet passing in front of it. “If you know the star’s size, you can figure out the planet’s size from the percentage of light that’s being blocked,” Ricker explains.

That task falls to the satellite’s four CCD cameras—precise photometers fabricated at MIT Lincoln Lab and on campus under the watchful eye of instrument manager Greg Berthiaume ’86. Vanderspek, meanwhile, is responsible for achieving the requisite stability and sensitivity of those cameras, charged with surveying 90% of the southern sky in TESS’s first year of operation and a similar portion of the northern sky a year later. Ricker estimates this will turn up approximately 3,000 “transit signals,” or instances of temporary dimming, of which 1,700 might be confirmed as planets by ground observations in the third year.

Leading the TESS science team are Harvard-Smithsonian astronomer David Latham ’61 and Sara Seager, MIT’s Class of 1941 Professor of Planetary Science and Professor of Physics, as well as an AeroAstro faculty member. Joined by new MIT physics assistant professor Ian Crossfield, they will select 100 candidates for follow-up observations, whittling that down to a list of at least 50 confirmed small planets, roughly Earth-sized, a subset orbiting within the host star’s “habitable zone” at a distance where surface water could exist in liquid form. The Hubble Space Telescope and successors like the James Webb Space Telescope would then train their sights on the exoplanetary “Top 50,” as would large ground-based telescopes. “We’ll definitely want to look at their atmospheres to check for the presence of gases—such as oxygen, water vapor, and methane—that may be associated with life,” says Seager.

TESS will complement NASA’s Kepler mission, which has already discovered more than 2,000 confirmed exoplanets within a small patch of sky. With its broader sky coverage, TESS can find planets about 10 times closer, circling much brighter stars, making it easier to determine their mass, density, composition, and other properties.

TESS joins other exoplanetary research underway at MIT. Julien de Wit PhD ’14, a postdoc in the Department of Earth, Atmospheric and Planetary Sciences who recently accepted an offer to join the MIT faculty, is part of an international team that spotted seven Earth-sized planets orbiting the star TRAPPIST-1. Seager, meanwhile, is the principal investigator of ASTERIA (Arcsecond Space Telescope Enabling Research in Astrophysics), a low-cost mission that’s set to launch a cereal box-sized satellite this year in the hopes of finding the best Earth analog yet. Says Seager, “We’re following any leads we can to learn more about exoplanets.”

At the same time, perhaps, sentient creatures on one of those worlds might be going through a similar exercise, trying to learn about Earth and its curious inhabitants.

Steve Nadis is a 1997–98 MIT Knight Science Journalism Fellow.


  1. David

    This is exciting. One question I have always had about the transit method is whether it will only work if Earth is in the “orbital plane” of that planetary system? It would seem that if Earth is a few degrees or more above or below the plane then we would not be able to observe the transit. Is this correct? If so, then what percentage of planetary systems can we observe by the transit system? 1%?

  2. Eduardo Ochoa-Castiello

    I think you are loosing your time looking for something that does not exist

  3. MIT Civil Engineer ´49, Dr. Biology, U. Bogota

    Congratulations on your ambitious project TESS. As Director of the Center for Environmental Biology (Bog0ta) I am interested in the question of possible extraterrestria life and wish to keep informed on the advances in your project.

  4. If climate change is coming, it is not too early to think about where humans might migrate or what others may have learned about how to fight global warming.
    Howard Martin BS in ChE, Class of 1953

  5. José María Larrauri Ucelay

    In the solar system, our own planet alone is suitable for surface life. But planets outside the solar system, with similar conditions to those of the Earth, regarding liquid water and temperature, may harbor macroscopic life on their surface.

    On the other hand, the subsurface conditions within many of the larger planetary bodies in the solar system may be similar to those of the Earth. The relationship of pressure and temperature with depth will be different, but presence of hydrocarbons and liquid water can be expected within them.

    The detection of atmospheric methane in all major solid planetary bodies, included the Moon and Mars, make it plausible the theory of upwelling abiotic hydrocarbons.

    The development of microscopic life, based on this energy source, would then be possible. Surface life, where conditions allow it, would be a development of subsurface life, and not the other way round.

    When Thomas Gold presented, in his 1992 paper, the “deep hot biosphere” idea, he suggested that “perhaps 10 planetary bodies in our solar system would provide suitable subsurface homes for fundamentally the same kind of life as we have within the earth”.

    He chose our Moon as the lower size limit for a subsurface biosphere, for smaller bodies “will probably fail to support liquid water even at depth”.

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