The surf report on Enceladus, and the weather report on Titan: Both mysterious with chance of bizarre.

The Cassini mission has been returning a lot of interesting data from the moons of the Saturn system, and on two of its most interesting worlds in particular: Enceladus and Titan.



Above: Teeny Enceladus and massive Titan float in space, together with Saturn's rings. Although when I say teeny I mean it the way astronomers use the word, which is to say 'hundreds of miles big'. Courtesy of NASA.

Enceladus, a tiny moon of Saturn with a warm sea at its south pole, has revealed another of its secrets: It may well have hydrothermal vents at the bottom of its seas. The little moon is one of the more helpful worlds in our solar system - its south pole is pierced by massive geysers that jet the seas (and any material in them) into space. This gives the Cassini spacecraft a chance to fly through the plumes and sample the sea. So far it had found salt, organic molecules.... and tiny particles of rock.

The rock particles are the clue that points towards deep sea vents on Enceladus: These particular particles need temperatures of at least 90 degrees Celcius to form. A second line of evidence that (possibly) suggests hydrothermal vents are present is the methane found venting into the atmosphere of Enceladus - hydrothermal vents are one of the possible explanations for the gas, with another being methane rich ices known as clatherates."This moon has all the the ingredients to support habitability in the outer solar system" Said Nicolas Altobelli, ESA's Cassini project scientist.

Above: To explain hydrothermal vents a bit better I give you David Attenborough. Because there's never a bad time for a David Attenborough clip. Unless there're angry crocodiles in the room with you, but then you probably shouldn't be reading this either.... Courtesy of the BBC.

 

Elsewhere in the Saturn system the giant moon Titan is revealing more mysteries. The only known moon with a substantial atmosphere, when the Cassini space mission began to pierce Titan's orange smog it found a world soaked in liquid natural gas, and covered in sands and soils made of organic compounds often too complex to identify. Speculation on what, if any, kind of life could exist there has recently been stoked by computer models of cryogenic cell membranes, and the discovery of odd chemical imbalances between the surface and atmosphere. The moon holds plenty of other things that are just plain mysterious, like the disappearing islands or why there've been no definitive sightings of waves on its seas.

Above: An island on Titan's methane sea appears out of nowhere. Once there the space penguins try to catch it with a giant red hula hoop. Not really, everyone knows space penguins can't stand red. Courtesy of NASA

Amid all this mystery and alieness you'd think that something as simple as the weather report would be a mere detail. But even here Titan throws curve balls - or, in this case, strange raindrops: Just as its seas and lakes are filled with liquid methane and ethane, so its rain is made of those things. Cassini, flying high above Titan, showed ground wetted by a recent methane rainstorm - a first but not that surprising. What was odd was what happened next: Parts of the surface started that were rained on started getting brighter, reaching a maximum weeks or months after the storm and staying that way for months. Then the brightened areas gradually shrank, reducing in extent, and eventually faded.

Why Titan's surface would react this way to rainfall isn't clear - it isn't  a chemical effect, although chemical weathering does happen on Titan.One possibility the paper describing all this raises is that the rain could have dissolved something in the soil which would wick upwards towards the surface then settle as a layer of crystals as the soil dried out. Over time the chemical would revert to its natural state in the soil - that'd explain why only certain areas were affected. Another possibility is that evaporation of the methane sitting on the surface after the rainfall cooled it enough for it to freeze as a long lived layer of tiny crystals.
And, this being Titan, there's always the possibility of something entirely unknown and weird going on...

The other bit of news from Titan - in a paper published by a lot of the same researchers as the first - is a possible detection of waves on the surface of one of its northern seas, Punga Mare.  The glassy calm of Titan's seas has been a serious head scratcher for scientists. Suggestions on why range from the seas being like syrup in texture, to actually being vast plains of jelly. As much as I like jelly the simplest explanation is that the winds,  for some reason,  simply haven't yet got strong enough to make waves. The paper's authors now think they're seeing signs of waves beginning to form as the northern seasons turn and the winds pick up, although they're not certain yet.

Above: In case you haven't heard of the Cassini mission here's a quick run down. Although I'm silently judging you for not knowing. I'm mean like that. Courtesy of NASA. 

Elsewhere in the solar system:
Evidence of a possible habitable zone on Mars isn't such big news these days, but a recent find underscores how world with lots of ice and any kind of volcanic heat can produce possible habitats fr life. Rising magma beneath a glacier field of may have heated areas where it breached the surface to make subsurface zones of warm water.

Arecibo strikes again:
Using its unique ability to send 'probes'  of radio waves to other worlds,  the giant radio telescope has returned sets of maps of Venus...  Years apart -  the team plans to use this method to check the Venusian surface for changes that might indicate active volcanoes or other processes.

Magnetic probe mission launches:

Magnetic reconnection is a process that turns magnetic energy into heat and results in some of the biggest and most inexplicable explosions in the universe -  in particular it causes flares on our own sun with the energy of millions of hydrogen bombs.  The Magnetic Multiscale  Mission, consisting of four spacecraft that will fly in formation through magnetic reconnection events in space and build up a picture of how these phenomena work, is designed to help us unravel this mystery.

 

Above: How the four satellites will deploy. The spacecraft have actually launched, but  couldn't find a video online yet, so we'll have to make do with this and some imagination. Courtesy of NASA

 

A cometary tale of survival?
ESA will begin attempts to recontact the Philae lander, which has been lost on the surface of comet 67P since November. The odds of the Rosseta mothership contacting the washing machine sized craft so soon are slim, but good enough to make it worth trying

Another moon with an ocean!
Ganymede, a moon of Jupiter, appears to have an ocean beneath its ice, similar to its sibling world Europa.

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