Scientists give message to anyone hoping for aliens on Venus: give up

Astronomers have speculated for decades that Venus could once have been remarkably similar to Earth – and might have been able to support life like our own planet

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Scientists have given a stark warning to anyone hoping that Venus might once have been home to alien life: stop.

For decades, astronomers have speculated that our closest neighbour might once have been much more like Earth than it is today. While it is a hot hell planet now, it might once have had its own oceans – and perhaps even supported its own life, some have suggested.

But new research suggested that it never had such oceans and as such was not habitable. While we can’t know for sure whether it can or did support life until we visit, the new findings suggest that it has always been a harsh environment for life.

That is based on findings that used information about the chemical composition of Venus’s atmosphere to try and understand the water content of its interior, which would indicate whether it ever had oceans. The researchers concluded that the planet currently has a substantially dry interior that is consistent with the idea that Venus was left desiccated after the epoch early in its history when its surface was comprised of molten rock - magma - and thereafter has had a parched surface.

Water is considered an indispensable ingredient for life, so the study’s conclusions suggest Venus was never habitable. The findings offer no support for a previous hypothesis that Venus may have a reservoir of water beneath its surface, a vestige of a lost ocean.

Volcanism, by injecting gases into a planet’s atmosphere, provides clues about the interior of rocky planets. As magma ascends from an intermediate planetary layer called the mantle to the surface, it unleashes gases from deeper parts of the interior.

Volcanic gases on Earth are more than 60% water vapor, evidence of a water-rich interior. The researchers calculated that gases in Venusian eruptions are no more than 6% water vapor, indicative of a desiccated interior.

“We suggest that a habitable past would be associated with Venus‘ present interior being water-rich, and a dry past with Venus‘ present interior being dry,” said Tereza Constantinou, a doctoral student at the University of Cambridge’s Institute of Astronomy and lead author of the study published on Monday in the journal Nature Astronomy.

“The atmospheric chemistry suggests that volcanic eruptions on Venus release very little water, implying that the planet’s interior - the source of volcanism - is equally dry. This is consistent with Venus having had a long-lasting dry surface and never having been habitable,” Constantinou added.

Venus is the second planet from the sun, and Earth the third.

“Two very different histories of water on Venus have been proposed: one where Venus had a temperate climate for billions of years, with surface liquid water, and the other where a hot early Venus was never able to condense surface liquid water,” Constantinou said.

The Venusian diameter of about 7,500 miles (12,000 km) is just a tad smaller than Earth’s 7,900 miles (12,750 km).

“Venus and Earth are often called sister planets because of their similarities in mass, radius, density and distance from the sun. However, their evolutionary paths diverged dramatically,” Constantinou said.

“Venus now has surface conditions that are extreme compared to Earth, with an atmospheric pressure 90 times greater, surface temperatures soaring to around 465°C (869°F), and a toxic atmosphere with sulfuric acid clouds. These stark contrasts underscore the unique challenges of understanding Venus as more than just Earth’s counterpart,” Constantinou said.

The story appears to have been different on Mars, the fourth planet from the sun.

Surface features on Mars indicate it had an ocean of liquid water billions of years ago. No such features have been detected on Venus. Mars, according to research published in August based on seismic data obtained by NASA’s robotic InSight lander, may harbor a large reservoir of liquid water deep under its surface within fractured igneous rocks, holding enough to fill an ocean that would cover its entire surface.

While Venus has been studied less than Mars, new explorations are planned. NASA’s planned DAVINCI mission will examine Venus during the 2030s from its clouds down to its surface using both flybys and a descent probe. Also during the 2030s, the European Space Agency’s EnVision orbital mission is due to conduct radar mapping and atmospheric studies.

“Venus provides a natural laboratory for studying how habitability - or the lack of it - evolves,” Constantinou said.

Additional reporting by Reuters