New Method for Discovering Extrasolar Planets

Researchers at the Instituto de Astrofisica de Canarias in Tenerife have captured spectroscopic information from light passing through the Earth’s atmosphere during a lunar eclipse that could greatly enhance our ability to discover extrasolar planets. This so-called “transmission spectrum analysis” provides information about the chemical constituents of a planet’s atmosphere. Now that the transmission spectrum of the Earth has been measured, it can be compared to other transmissions in order to identify similar patterns which may emanate from life-bearing planets.
 An artist's rendition of the sunlight shining through the Earth's atmosphere as seen from the moon (Source: Gabriel Perez Diaz, Instituto de Astrofisica de Canarias)
An artist’s rendition of the
sunlight shining through the
Earth’s atmosphere as seen
from the moon (Source: Gabriel
Perez Diaz,Instituto de
Astrofisica de Canarias)

According to the scientists working on the project, the recorded spectrum contained unmistakably strong signs of life as well as some other unexpected molecular information about our planet and the signature of its Ionosphere. This data is very specific and distinct, and the examination of the spectrum showed a great deal of information regarding the biological processes occurring on the planet as well as its chemical composition.

Astronomers have discovered hundreds of extrasolar planets in the past several decades. As observatories improve their resolution and distance, scientists anticipate the discovery of a great deal more of these including many Earth-sized planets. Some of them, they say, will likely orbit within the basic habitable zone of their stars. Capturing their transmission spectrums should help astronomers further identify those planets that are most likely to contain native life forms. Of course, there is no guarantee that such planets will actually host inhabitants or that ones, which do not have an Earth-like spectrum won’t host life of some kind. Furthermore, capturing the transmission spectrum of these distant planets presents its own challenges. Still, the new method provides a way for narrowing down the entire set of discovered planets to those most likely to house life.

Scientists were surprised by some of the results of the transmission spectrum. Methane is only present in the Earth’s atmosphere in trace amounts but it features prominently in the spectrum. This implies that planets with even tiny amounts of methane in their atmosphere could be identified using this method.
The spectrum also showed molecules that scientists didn’t expect to show up despite their presence in the atmosphere. Thus, these results may also provide previously unknown information about the Earth in addition to assisting in the search for extraterrestrial life.

The experiments were carried out at Roque de los Muchachos Observatory using the Nordic Optical Telescope and the William Herschel Telescope. These leveraged the alignment of the Sun, Earth, and Moon being in a straight line during a lunar eclipse to use the Moon as a mirror reflecting back the image of the Earth’s atmosphere for analysis.

TFOT has previously reported on the search for extraterrestrial life in this video featuring Dr. Michio Kaku and on carbon films that might help IBEX search for extraterrestrial life. TFOT has also explored space chemistry including the discovery of carbon dioxide by the Hubble Space Telescope, a first look at the chemical composition of Mercury from NASA’s Mercury Surface, Space Environment, Geochemistry and Ranging spacecraft, and the Spitzer Space Telescope’s discovery of organic gases and water vapor around an infant star.

Read more about the new method for discovering Earth-like planets in this Instituto de Astrofisica de Canarias news release.