Canadian astronomers develop fingerprint of Earth's atmosphere

Astronomers at Canada's McGill University have made a "fingerprint" for the Earth, which could be used to identify a potentially life sustaining planet beyond the solar system.

Using over a decade of observations of the Earth's atmosphere taken by the SCISAT satellite, McGill Physics student Evelyn Macdonald, and her supervisor Prof Nicolas Cowan have constructed a transit spectrum of Earth - a detail on the fingerprint-like unique composition of our planet's atmosphere.

The findings of the work were published in the science journal Monthly Notices of the Royal Astronomical Society on August 28, and can help scientists determine the kind of signals called 'biosignatures' that astronomers need to look out for in order to find Earth-like planets outside our solar system.

The fingerprint includes the simultaneous occurrence of both ozone and methane, which happens only when there is an organic source of these compounds on the planet, says the study.

"A handful of researchers have tried to simulate Earth's transit spectrum, but this is the first empirical infrared transit spectrum of Earth," says Prof Cowan. "This is what alien astronomers would see if they observed a transit of Earth."
"TRAPPIST-1 is a nearby red dwarf star, which makes its planets excellent targets for transit spectroscopy. This is because the star is much smaller than the Sun, so its planets are relatively easy to observe," explains Macdonald. "Also, these planets orbit close to the star, so they transit every few days. Of course, even if one of the planets harbours life, we don't expect its atmosphere to be identical to Earth's since the star is so different from the Sun."