It's likely that Venus was always hell and never had oceans.

According to a new study, there is not enough water vapor in the seething mass of carbon dioxide that makes up the Venusian atmosphere to support the suggested rainy history. If confirmed, the study would imply that it is pointless to look for evidence of extinct oceans on Venus. It might also make us wonder if research on planets surrounding other stars that are warmer than Earth should be given less priority.

Observing Venus' clouds, science fiction authors envisioned a world with swamps and oceans below—unpleasant, maybe, but habitable. Not everyone gave up when probes showed temperatures hot enough to melt lead; some believed Venus used to be like that but that it was just too late. Some contend that the planet directly opposite Earth was just as conducive to life 4 billion years ago. If so, our telescopes may be best suited to target similar worlds at an earlier stage of development.

Unfortunately, three scientists from Cambridge University come to a conclusion. Venus should be more of a steam bath than the hyper-Atacama missions have shown, but if that were the case, a runaway greenhouse effect may make it excessively hot.

This is not a novel idea for the three of them. Two competing histories of Venus have been going on for some time. One is Venus, a once-hospitable planet destroyed by a runaway greenhouse effect—albeit a natural one rather than the result of a polluting civilization—and serves as a warning. It has always been hot and dry in the other.

For each, arguments have been made. Because of Venus's high deuterium concentration, some scientists believe that the planet formerly contained a lot of hydrogen that has since escaped, which may have created oceans hundreds of meters deep. However, various theories have been put up.

Tereza Constantinou, a PhD candidate, felt a fresh perspective would end the impasse. "We wanted to take a different approach based on observations of Venus’ current atmospheric chemistry, even though both of those theories are based on climate models," Constantinou said in a release. Since the planet's interior and exterior are constantly in chemical communication with one another, any chemicals that are taken out of the atmosphere need also be added back to maintain the stability of the Venusian atmosphere.

Steam is actually the main product of Earthly volcanoes, despite the fact that we typically conceive of them as releasing ash, carbon dioxide, and sulphurous gases. Entering an environment that is already heavy with water vapor makes that less obvious. If Venus's interior contains even a small amount of water, some of it should be able to escape through the volcanic activity that we can nearly be positive is still occurring.

Even when water is a gas, the conditions in the Venusian atmosphere are not favorable for its long-term survival. However, water vapor should make up a significant amount of the atmosphere if Venus' volcanoes are generating as much of it as carbon dioxide and carbonyl sulphide.

Constantinou and co-authors believe that little more than 6% of water must be ejected from Venus' volcanoes, based on evidence from our probes and the anticipated lifespan of various gases. Any water that Venus may have had at the beginning would have departed extremely quickly since its interior would have much less water than Earth's mantle.

“We won’t know for sure whether Venus can or did support life until we send probes at the end of this decade,” Constantinou added. "However, it is difficult to imagine Venus ever supporting Earth-like life, which requires liquid water, given that it probably never had oceans."

The gradual cooling of Venus's initial surface magma, which gives water more time to escape, is the reason given by the authors for the water loss. If that is the case, it may have been motivated by some unique Venusian rationale, but it is more likely to be a reflection of characteristics shared by planets at what we now regard as the inside border of the habitable zone.

That would influence how we looked at life throughout the ensuing decades. According to Constantinou, other planets we have already discovered might also be habitable if Venus was habitable in the past." But as she pointed out, our existing telescopes and those that are being planned perform best on planets that are closer to their star than Earth is, so we intend to concentrate their attention there. But if Venus was never livable, then planets that resemble Venus elsewhere are less likely to have life or habitable conditions, Constantinou continued.

"It's kind of sad to find out that Venus wasn't a planet much closer to our own, because we would have loved to find that it was," Constantinou added. But in the end, it's more beneficial to concentrate the search on planets that have the highest probability of supporting life, at least life as we know it.