IAC press release
Lunar eclipse observations help find new Earths
A team of researchers from the Institute of Astrophysics of the Canary Islands (IAC) has studied for the first time the transmission spectrum of the Earth reflected in the Moon, as a reference measure for the search for life on other planets outside the Solar System. The method consists of analyzing the Earth's atmosphere as if it were a distant planet, seeing what its main biological markers are (oxygen, carbon dioxide, water, methane, etc.) and extrapolating the results to the new planets that are discovered, comparing if the ideal conditions exist for life to exist.
"Until now there were only models that explained what the terrestrial spectrum was like, we have made the first real measurement through a lunar eclipse", declares Enric Pallé, an IAC researcher involved in the work. In other words, scientists have taken advantage of the fact that the Sun, Earth and Moon were aligned in this order to begin their study. Only then, sunlight passes through the Earth's atmosphere and reaches the Moon. In other words, if you were on the Moon in full eclipse, you would see the silhouette of the Earth, opaque, surrounded by the spectrum of a ring of illuminated atmosphere. It could be said that the Moon has been used as a mirror in which to observe the characteristics that allow life on our planet. These measurements have been made from the Roque de los Muchachos Observatory (La Palma) and using the Nordic Optical Telescope and the William Herschel.
"Until now, transit through spectroscopy was the ugly duckling among the techniques proposed to characterize the atmospheres of habitable planets, now the duck has become a swan," says Rafael Barrena, astronomer at the IAC. Without a doubt, this is good news for future missions that will search for life in the universe. Characterization of an extrasolar planet can lead to a complete understanding of its chemical composition, formation, and evolution.
the first fruits
“The basic conclusion of our work is that the characterization of the atmospheres of extrasolar planets, and the search for life outside the Solar System, may not be as difficult to achieve technically as previously thought”, concludes Eduardo L. Martín, an astronomer at the IAC. According to the researchers, the results were surprising. Not only were the fingerprints of the main biological markers (water, CO2 and oxygen) present in the spectrum, but also these marks were unmistakably strong. "They are seen as very marked features, that is, it will be much easier to identify them on an extrasolar planet than was initially thought," explains María Rosa Zapatero Osorio, an astronomer at the IAC.
In this sense, one of the novel results of the research is that methane, barely present in the atmosphere, becomes a prominent feature. In other words, if there is methane on an extrasolar planet, however little it may be, it will be detected very easily. In addition, it should be noted that a number of other features have been observed that point to the presence of nitrogen, which makes up 80 percent of the Earth's atmosphere. "The results tell us that there is much room for improvement in our understanding of the Earth, and as has happened with the newly discovered giant extrasolar planets, there is always some room for surprises and unexpected results," says Pilar Montañés-Rodríguez, a researcher at the IAC.
a matter of time
The last two decades have seen the discovery of hundreds of extrasolar planets and more and more missions, both from Earth and in space, are dedicated to their search. Once these planets are found, efforts are concentrated on their study and characterization to see if they have the right conditions for life.
Most of the discoveries of extrasolar planets have been produced by drawing attention to the effects that they have on the star around which they orbit. In this sense, when a celestial body passes in front of a star, its light passes through the planetary atmosphere and is modified by the chemical compounds it contains (nitrogen, oxygen, methane, etc). If the spectrum of the star is studied before and after the planet transits through it, the transmission spectrum of the planet is obtained, or what is the same, its atmosphere can be studied.
The researchers say they now have a much better idea of how to find and recognize Earth-like planets where life is possible. The study has been published in the prestigious journal 'Nature' and the IAC researchers Enric Pallé, María Rosa Zapatero Osorio, Pilar Montañés-Rodríguez, Rafael Barrena and Eduardo L. Martín, who also belongs to the Department of Physics, have participated in it. from the University of Florida.