Enceladus: a song of ice and tides

An artist impression of Cassini diving into Enceladus water plumes. credit: NASA/JPL

Cassini will terminate its 20-odd-years-long mission in September. But it’s determined to go out with a bang. In yesterday’s press conference, NASA announced that the probe, during a 2015 flyby of Saturn’s moon Enceladus, found clues that the ocean within the icy moon has almost all we think it needs to spark life. Continue reading


Water on Mars! Sometimes!

A long time ago Mars had water on its surface, and maybe even oceans–we knew that. But now we‘re sure think that a little water still flows there. Sometimes. Kinda.

On September 28, NASA gave a big-time press conference, with a public livestream, to announce they found proof of something people suspected for a while: water flows on Mars.

The Mars Reconnaissance Orbiter probe collected pictures of slopes, where long streaks stretch and shrink seasonally.

Because they conspicuously resemble small water streams, scientists studied them combining the great images from the HiRISE telescope on board the probe with spectroscopic measurements (which measure different light wavelengths to determine the chemical composition of a material).

The result is that these streaks (called Recurring Slope Lineae, or RSL) have all the makings of being caused by water flowing.

But RSLs are likely more similar to mud than water. Since Mars is really cold (-63 Celsius on average), the only way for water to prevent freezing is to have enormous concentrations of salt. The most probable candidate is perchlorate, which is almost everywhere on the planet surface. And it’s very toxic.

So don’t quite picture these as happy little mountain streams. They’re more like small avalanches of killer mud.

It’s also totally unclear where the water comes from. One possibility is that a thick layer of ice just below the surface thaws in the summer. Another is that there are actual underground waterbeds on Mars. Or maybe the water comes from the atmosphere, and the perchlorate captures it to the ground.

It may not look like much, but until now Earth was the only planet we knew with liquid surface water. This is a big step to figure how water works in the solar system.