Beyond the Sun: On The Hunt For Earthlike Worlds

Thomas Hearty and Inseok Song have hit on an approach that may one day lead to the discovery of Earth-like worlds.

Imagine being far out in space and looking back at Earth. Are there characteristics that could be deduced about our home planet even as a distant fuzzy ball? Thomas Hearty and Inseok Song think there might be. Thomas, a scientist at the Jet Propulsion Laboratory and Inseok, an astronomer at the Gemini Observatory in Hawaii, are using AIRS data to create spectra of the entire Earth as it would be seen by a distant observer. They believe that by examining the signature our own planet makes, we can come closer to understanding the signatures that other planets make. The two will be using what they find to help define requirements for the Terrestrial Planet Finder, a mission aimed at detecting Earth-like planets around other stars.

Previous whole-Earth spectra have been constructed indirectly using "Earthshine", i.e., reflected light from the dark side of the Moon. But this approach has only been able to produce spectra in the optical and near-infrared regions and is limited to edge-on viewing angles. Although some low-resolution spectra of the whole Earth have been obtained in the mid-infrared using the Thermal Emission Spectrometer onboard the Mars Global Surveyor, AIRS spectra are the first directly observed high-resolution infrared spectra that span all four seasons. Because AIRS also provides spatial information, its spectra can be weighted to simulate the spectra of extra-solar planets that could be similar to Earth. If Earth was a desert planet, what would its spectral signature look like? If Earth was an ocean planet or snow-covered, what would we see? The data from AIRS may one day provide an important clue in interpreting the characteristics of planets beyond our solar system.

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Written by: Sharon Ray, Jet Propulsion Laboratory

Science content provided by: Thomas Hearty, Jet Propulsion Laboratory