Venus is one of the most inhospitable places in the solar system where the temperature at the surface can melt lead and the atmospheric pressure is crushing. It is not a world where scientists expect to ever find life, but the evidence continues to grow that it may not have always been that way. As recently as several hundred million years ago (in geological terms), Venus may have had oceans, according to new research. What is now a searing hot hellhole was perhaps once very wet, and, just possibly, had conditions suitable for life.
The subject of water on Mars is one of the most highly debated in planetary science; various missions have provided ample evidence that the planet used to be a lot wetter than it is now, with rivers, lakes and maybe even oceans. Most scientists now generally agree on this, but as to how much water there was, how long it lasted and how warm the environment was, is another question. There have been apparent conflicting lines of evidence, and now findings from the Curiosity rover have only added to the mystery. Curiosity has revealed a paradox of sorts – it has found abundant evidence for ancient lakes in now-dry Gale crater, but at the same time has not found evidence for a previous thicker atmosphere with more carbon dioxide, which normally would be needed for water to remain liquid on the surface. These two lines of evidence seem to contradict each other, so how to resolve this puzzle?