Astronomer Jane Greaves of Cardiff University was alone in her office when she saw the signal: a fingerprint from the molecule phosphine, hanging out in data she’d taken of Venus’ atmosphere back in 2017.
You’ve probably never heard of phosphine, and so don’t know why its existence on a nearby planet would stun an astronomer, as it did Greaves. But some scientists think phosphine—a humble pyramid of three hydrogen atoms bonded to a phosphorus—may be a useful biosignature: a sign, if you see it on a solid-surface terrestrial planet, that life might live there.
It was possible, though unconfirmed, that Greaves had just caught the first glimpse of alien beings. She wandered around in a daze.
The hour was late and everyone else had gone home. “There wasn’t really anyone to tell,” she says. Cautious of jumping to conclusions, she stifled her excitement and commanded herself to do normal things, to focus on the business of living. So she left work and went to the grocery store. “Must find food, must do something sensible, must not crash the car,” she recalls telling herself on that evening in late 2018.
“Being British, I had to buy the ingredients for curry,” she adds. A celebration.
She spent the next few days checking that she hadn’t made a mistake. The signal, which sure looked like phosphine, persisted. And today, after many more months of data gathering and analysis, she and a team of colleagues made the official announcement: There appears to be phosphine on Venus, and so far they’ve found no explanation for why it might be there—except as a result of Venusian life.
That doesn’t mean there is life on Venus. Some nonbiological process unknown on Earth might have churned the molecule into existence. Humans have, after all, cried “Aliens!” because of suspicious chemistry before. But while there’s much followup work to be done—many complications, confirmations, or denials that could and probably will come—it’s also possible today’s the day humans are introduced to the ultimate other…
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