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Planetary Scientists Say It's Time To Explore Venus

ARI SHAPIRO, HOST:

Right now, three missions from Earth are headed to the planet Mars. But some planetary scientists say the time has come to look at another of Earth's neighbors - Venus. NPR's Geoff Brumfiel has more on why Venus is getting attention.

GEOFF BRUMFIEL, BYLINE: Venus is actually the first planet where humans ever landed a probe.

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UNIDENTIFIED PERSON: (Non-English language spoken).

BRUMFIEL: Fifty years ago, the Soviet Union sent its Venera 7 lander through Venus' clouds.

MARTHA GILMORE: The Venus atmosphere is so thick, it's almost like you can float down. It's thick enough that you can just sort of gently land on the surface.

BRUMFIEL: Martha Gilmore is a planetary scientist at Wesleyan University who studies Venus. The landing was smooth. But after that, it got tough. The probe faced pressures like those deep under the ocean, temperatures of around 900 Fahrenheit. It only lasted about an hour and a half.

GILMORE: Before suffering what we call a thermal death.

BRUMFIEL: That's science speak for saying it fried on Venus' harsh surface. But the data it sent back combined with data from other landers and orbiting satellites that went to Venus in later decades have taught us a lot about the planet. And scientists now believe that a few billion years ago, Venus would have looked very different.

SARA SEAGER: Venus started out, we all believe, as, like, a pleasant place...

BRUMFIEL: Sara Seager is at MIT.

SEAGER: ...With nice temperatures at the surface, with a liquid water ocean like Earth still has today. Maybe it had blue skies and water clouds. And then something went horribly wrong with Venus.

BRUMFIEL: The best guess is that carbon dioxide from volcanoes on the surface triggered a runaway greenhouse effect. That, combined with Venus' nearness to the sun, made it get hotter. Oceans evaporated, and it warmed still more until it became the hot, hostile Venus we see today. Sue Smrekar is a senior research scientist with NASA's Jet Propulsion Laboratory. She currently helps lead a small mission on the surface of Mars, but she'd also like to get back to Venus.

SUE SMREKAR: Sometimes, people ask me - I get tongue-tied because I feel like there's, like, so many reasons to go to Venus.

BRUMFIEL: Volcanoes, geology. But for Smrekar, it really comes down to Venus' resemblance to the Earth.

SMREKAR: How did these two planets that are so similar in size, distance from the sun and probably very much alike at the beginning of their evolution - how did they become so different?

BRUMFIEL: And Martha Gilmore says the biggest question of all is - could life have started on Venus like it did on Earth?

GILMORE: I mean, this is the question we have of all of the worlds in the solar system that we explore. Was it habitable? And then what follows is - was it inhabited?

BRUMFIEL: With revelations about ancient oceans, the answer to that first question is leaning towards yes. And just recently, there was a finding that suggested life might live on Venus today. Sara Seager and collaborators found evidence of a chemical called phosphine in the atmosphere, something that could be explained by microbes living in the clouds of Venus. Seager says the phosphine signal is still tentative and needs to be followed up. But Gilmore says regardless of the outcome, the research has focused people's attention on Venus.

GILMORE: I am happy that we've all thought hard about Venus and about this possibility. That's how science should work. So let's go to Venus. Let's go.

BRUMFIEL: There are now several missions being proposed to go to Venus; although, some of those missions are in competition with trips to other cool destinations - moons of Jupiter and Neptune. NASA could make a final decision as soon as early next year.

Geoff Brumfiel, NPR News.

(SOUNDBITE OF YEAH YEAH YEAHS SONG, "DRAGON QUEEN") Transcript provided by NPR, Copyright NPR.