Our planet is like Venus in a number of ways. The two are exceedingly similar in size and mass, for example; however, despite being so identical in relation to these measurements, Venus has high temperatures—reaching up to 427°C (800°F), which would kill most all life on Earth. Venus also has very little water, about 100,000 times less than the Earth’s water. Ultimately, this makes Earth’s "sister planet" incapable of harboring life.
But some researchers say that this hasn’t always been the case.
Venus May Have Been a Waterworld Before
Venus Express —the spacecraft launched by European Space Agency to Venus — has confirmed that the planet, over the course of its evolution, has lost large quantities of water into space via ultraviolet radiation that eradicated water through the atmosphere.
It has also shown that deuterium, a heavy form of hydrogen, was abundant in Venus’ atmosphere, which suggests that the planet once consisted of great amount of water that was lost over time. As such, researchers say that is possible that Venus had large bodies of oceans that made it habitable in previous eras.
Michael Way, at the NASA Goddard Institute for Space Studies in New York City, noted in a statement that the evidence is intriguing, but not yet conclusive, “There’s great uncertainties in understanding Earth, not only its climate history but the history of how life began. There’s no reason that life on this world would not have existed in these oceans [Venusian oceans]. But that’s about all you can say.”
Exploring Venus Further
In order to determine exactly how much water the planet previously had, and whether or not it could have sustained life at any point, NASA is planning a number of different missions.
One such mission would involve actually traveling to the surface of the planet—dropping a probe through the clouds—and the other would orbit around the planet and image its surface to search for relevant signs.
Specifically, NASA plans to send VERITAS to investigate how similar Venus is to our home planet and, as NASA notes, create "global, high-resolution topography and imaging of Venus' surface and produce the first maps of deformation and global surface composition."