Eclipsing Earth

International study could aid search for life in the universe

A lunar eclipse helped a group of international scientists take a snapshot of Earth’s chemical fingerprint, which could help to identify planets most similar to Earth where life may be thriving.

An artist’s rendering of Professor Martin’s research.
Photo: Instituto de Astrofísica de Canarias, Spain

University of Central Florida Associate Professor Eduardo Martin was a member of the team that made the observation, which is published in the June 11 edition of Nature magazine.

The team used some of the world’s largest optical and infrared telescopes located at the Roque de los Muchachos Observatory in La Palma (Canary Islands, Spain) to observe light reflected from the Moon toward the Earth during a lunar eclipse on August 16, 2008.

The eclipse provided team members with a unique opportunity to mimic what they could observe if they were watching the Earth pass in front of the Sun from an extraterrestrial observatory. When a planet passes in front of a star, part of the starlight passes through the planet’s atmosphere. That light contains the chemical composition of the planet and is called the transmission spectra of a planet.

The chemical composition describes what makes up the Earth and what makes it habitable to humans. Scientists expect planets similar to Earth to bear a similar chemical composition. The snapshot the team took gives NASA and other space agencies a list of ingredients to look for when evaluating newly discovered planets. If a new planet has similar ingredients in the right proportion, then it would be a good target for further exploration.

"Now we have a much better idea about what to do to find planets similar to our own where life may be thriving," Martin said. "The greatest reward will happen when one of those planets shows a spectrum like that of our Earth."