NASA Strategic Roadmap: The Search for Earth-like Planets

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Executive Summary

“Is there life elsewhere in the Universe?”, “Are there other planetary systems like our own?, “How do planets and stars come into being?”, “Are we alone?”. In the vast blackness of the Universe, our home planet is a sparkling oasis of life. Whether the Universe harbors other worlds that can support life is a question that has been asked for millennia. However, we are privileged to live in a time marked by scientific and technological advances so rapid and so brilliant that these elusive questions can now be pursued not only with philosophical speculation, but also with scientific observation. While the questions are simple, the scientific and technical capabilities needed to answer them are challenging. In this Roadmap, we articulate the scientific case for exploration beyond the Solar System and map out a set of implementing strategies and missions that will lead to the answers to these and other central questions concerning humanity’s place in the Universe. This Roadmap is a framework for Exploration on the grandest scale, leveraging NASA’s considerable experience to achieve what only NASA can. It is an answer to NASA’s Vision “… To find life beyond.” It is the response to NASA’s Mission statement ” … To explore the Universe and Search for Life” and ” … To Inspire the Next Generation of Explorers.” If fully implemented, it would be the partial realization of the Space Exploration Vision, as described in the “President’s Commission on Implementation of United States Space Exploration Policy,” which challenges NASA to Search for Earthlike Planets. “The President’s Vision for United States Space Exploration (2004)” has made the “advanced telescope searches for Earth-like planets and habitable environments around other stars” one of the foundations of NASA’s exploration goals.

Our central theme is the quest for Earth-like planets, habitable environments, and signs of life outside the Solar System. To fully realize this vision requires measurements in both the visible and the infrared, and the determination of planetary masses. Therefore, we have designed a staged program of space missions, Kepler, the Space Interferometry Mission (SIM), the Terrestrial Planet Finder-Coronagraph (TPF-C), the Terrestrial Planet Finder-Interferometer (TPF-I), and Life Finder, each building on the legacy of and information derived from the previous one. Kepler will find signs of terrestrial planets shadowing distant stars; SIM will measure the motion of nearby stars caused by planets, and the masses of those planets; TPF-C in optical light will image a dim Earth from under the glare of its bright companion star and probe its atmosphere; TPF-I, the even more sensitive infrared counterpart to TPF-C, will extend these studies in detail and range; and, finally, the spectroscopic telescope, Life Finder, will study the atmospheres of even more distant planets to seek definitive evidence of life. Planets and planetary systems are

formed in the context of stellar birth. This Roadmap describes the mysteries of formation and birth and explains how missions such as the James Webb Space Telescope (JWST), the Stratospheric Observatory for Infrared Astronomy (SOFIA), and the Single Aperture Far-InfraRed mission (SAFIR) will unravel them. Each mission in this ambitious series builds on the technological and scientific legacies of those that precede it.

A guiding principle is that the flagship missions must represent quantum leaps in performance. JWST will be 100 to 1000 times as sensitive as Spitzer. It will have 10 times the collecting area of Hubble. In the far-infrared, SAFIR will be more than 100 times as sensitive as SOFIA. TPF-I will have 100 times the contrast capability of JWST, and TPF-C will have 10 5 times that of Hubble. With all these missions, the opening up of new “discovery spaces” is a major theme. What energizes the explorations described in this Roadmap is not only that known territory will be probed deeply and with precision, but that unanticipated new territories must inevitably be revealed.

It is crucial that investment for a mission reduce the risks and costs of its successor missions. Detectors in the far-infrared developed for SOFIA will pave the way for those on SAFIR. Cryogenic research for Spitzer and JWST will lead to the low-temperature capabilities necessary for TPF-I, SAFIR, and Life Finder. Interferometric capabilities for SIM will be incorporated into technologies needed for TPF-I and Life Finder. Advances in large telescope apertures for JWST will also be employed for the TPFs, SAFIR, and Life Finder. In the realms of detectors, telescopes, coolers, and distributed spacecraft, technology for a given mission must pay off multiple times in subsequent missions. Therefore, an integrated plan of crosscutting technology investment is one of the pillars of this Roadmap.

Beyond the strategic space missions, NASA’s scientific success depends on rapid and flexible response to new discoveries, inventing new ideas and theoretical tools leading to tomorrow’s space science initiatives, converting hard-won data into scientific understanding, and developing promising technologies that are later incorporated into major missions. These activities are supported through a balanced portfolio of competed Research and Analysis (R&A), Universe Probe, and Discovery programs, which collectively are designed to guarantee the continued vitality of NASA’s overall space science vision, reduce major mission risks, and optimize the return on NASA’s capital, technology, and manpower investments. Importantly, NASA, through its Education and Public Outreach programs and through the R&A program’s support of student and postdoctoral researchers at America’s universities, plays a critical role in educating the Nation and training the next generation of explorers.

Some of the discoveries to emerge from this Roadmap could fundamentally shift our understanding of our place in the Universe, with implications as profound as the early work of Copernicus, Kepler, and Galileo. A viable Roadmap must take full advantage of this potential to ignite the public imagination, while fulfilling its obligation to inspire the students of the future who will carry out its programs of discovery. This Roadmap is a legacy to them.