spaceSpace and Physics

Astronomers Discovered Life On Earth In An Important Test For Finding Habitable Worlds


Jonathan O'Callaghan

Senior Staff Writer

OSIRIS-REx pointed its instruments at us in late 2017. NASA's Goddard Space Flight Center Conceptual Image Lab

Scientists have used a NASA spacecraft to search for life on Earth, and found promising signs that we’re really here. Hooray!

That spacecraft was OSIRIS-REx, which is currently on its way to a skyscraper-sized asteroid 225 million kilometers (140 million miles) away called 101955 Bennu. But to get there, it performed a flyby of Earth in September 2017 that was 22 times closer than the Moon, giving it a boost from our planet’s gravity.


As it did so, it pointed its instruments towards Earth, mostly to check they worked. But using this data, scientists were able to study our planet from afar, building on similar work done with the Galileo spacecraft on its way to Jupiter in 1990, as first reported by Science Magazine.

“From the OSIRIS-REx fly-by, observers otherwise unfamiliar with the Earth could conclude that the planet is covered with large amounts of water,” the authors, led by Dante Lauretta from the University of Arizona in Tucson, principal investigator on OSIRIS-REx, wrote in their results. These were presented at the Lunar and Planetary Science Conference in The Woodlands, Texas, last week.

The team were also able to spot chemical imbalances in our planet, which could be signs of life. For example, the high levels of methane, oxygen, and ozone spotted suggested there was life on our planet. And they could see that light was being absorbed, a sign of photosynthesis.

Back in 1990, this experiment was first done with the Galileo spacecraft at the behest of the late astronomer Carl Sagan. Somewhat worryingly this time around, though, OSIRIS-REx detected levels of methane and carbon dioxide that were 12 and 14 percent higher than in 1990.


This would indicate that “the sources of these gases had accelerated their output over the past 27 years,” the authors note, due to pollution.

While a fun test, this study had an important point too. We really want to try and find planets outside our Solar System (exoplanets) that might be able to support life. And what better way to test our techniques than by practicing on the only world we know to have life?

“The ultimate goal of exoplanet remote sensing is to detect atmospheric biosignatures remotely,” the authors noted. If we can find life on our own planet, well, maybe we’ve got a chance of finding life elsewhere.

[H/T: Science Magazine]


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