There have been some interesting news stories recently about ancient water here and on Mars. They are hard to describe in plain English, though–at least in a single post.
Spread out over two or three posts, with lots of videos, it’s easier to follow this water.
First, let’s start up the Solar System:
Any water that was present near the Sun disappeared when this star fired up. Back then, the neighborhood was hot enough to vaporize carbon, let alone boil away any oceans that tried to form. Indeed, as Mercury, Venus, Earth, and Mars took shape, they must have lost several elements through vaporization, including hydrogen.
And without H you can’t have H2O.
Obviously water got to Earth somehow. Scientists thought for a long time that it arrived via comets–basically, big dirty snowballs that reside in the outer reaches of the Solar System. Impact by impact, according to this hypothesis, our planet collected water after the new Sun had settled down a bit.
But when the European Space Agency intercepted a comet in 2014, they discovered that its water had a different isotope “signature” than ours.
This complicated things. Then, in 2017, scientists learned that a certain type of meteorite called angrite contains water (not sloshing around but locked inside the rock).
That’s the important thing you should take away from this post: there can be water inside rocks, as well as flowing around them (like groundwater) or over them (like a stream).
These water-containing angrite meteorites formed very soon after the Sun did, apparently far enough away from the brilliant new star to avoid getting cooked. Which brings us to the first really cool news recently.
A huge collision happened in our neighborhood, forming the Earth and the Moon:
This isn’t news, although the details are still being worked out. But get this–even at that early point, the part that became Earth may have already had at least 70% of its present water!
It’s hard to believe, but water can be locked up in rock, even when it’s molten after an impact.
So there’s no particular reason to expect that all of a planet’s water is on its surface. This points toward some other scientific headlines lately about water deep inside the Earth–and possibly even within the apparently bone-dry planet Mars.
To be continued
Featured image: Pacific Ocean, from the International Space Station, NASA via Wikimedia.