I have recently seen a lot of articles discussing the so-called ocean worlds – that is, all planets and celestial objects that are not the Earth – and the interest in them is obvious: water is one of the essential elements of life (at least of the type we are familiar with).
And we’ve started to realise that Earth is by no means the only one. We’re literally encircled by them, starting with usual suspects in the Solar System – Europa and Enceladus.
But there far more than that, as the amazing page by NASA, Ocean Worlds, shows well.
Let’s take Ganymede, for example, another Jupiter’s moon like Europa – the largest moon in the solar system and the only moon with its own magnetic field. Recent studies have found a large underground saltwater ocean, probably trapped in the form of ice between its crust and core.
Water, however, might have come from farther away. One interesting theory relates that over billions of years, comets and asteroids have collided with Earth, enriching our planet with water. Maybe something was already there, or maybe not, but for sure the chemical markers we have so far identified in the water of our oceans suggest that most of the water came from asteroids. Also, we have some strong evidence that ice, and possibly even liquid water, exists in the interiors of asteroids and comets.
But we have also ocean worlds that have been lost, like Venus, for example. “Venus may have been our solar system’s first ocean world. Venus lacks a strong global magnetic field, which on Earth, helps to protect our atmosphere. A runaway greenhouse effect raised temperatures enough to boil off the water, which escaped into space due to the solar wind.” [Quoted from the NASA website]
Mars tells very much a similar story. “Mars was once much more Earth-like, with a thick atmosphere, abundant water, and global oceans. Billions of years ago, Mars lost its protective global magnetic field, leaving it vulnerable to the effects of our Sun: solar wind and space weather. The MAVEN mission has measured Mars continuing to lose its atmosphere to the Sun at the rate of nearly 400 kilograms per hour. Scientists estimate that Mars has lost approximately 87 percent of the water it had billions of years ago.” [Ibid]
This alone seems one good reason for studying our climate change patterns with a lot of attention, as NASA is currently doing now.
Finally, this is a good sciencecast about this topic. Happy watching!