Thursday, February 19, 2009

Liquid Water On Mars

Well, maybe. Within a couple of days of each other, reports of two possible evidence for liquid water on the red planet. The first shows blobs on the legs of the Phoenix lander that grew and changed shape and position, just like drops of water. The second suggests that a recently-formed gully that resembles those carved by running water may have been created by brines bursting from a point in the surface. The surface of Mars is colder than the freezing point of water, but high concentrations of chemicals - perchlorates in the case of the droplets on the Phoenix lander; ferric sulphate in the case of the brines that may have formed the gully - could act as anti-freeze and reduce the evaporation rate. So much for Bradbury's crystalline canals - this stuff would be more like the sludge that leaks out of toxic waste dumps.

Unfortunately, the concentrations of salts necessary to keep water liquid at minus seventy degrees Centigrade would rule out the possibility of life as we know it. "If you tried to put any kind of life-form you can imagine on Earth in a brine solution of that sort, the water would be sucked out of the cells," according to Phoenix mission leader Peter Smith. Yeah, but what about life as we don't (yet) know it?

Meanwhile, the Dawn probe has just swung past Mars on its way to the asteroid Vesta, boosting its velocity and fractionally slowing the planet.
"The flyby will cause Mars to slow in its orbit enough that after one year, its position will be off by about the width of an atom. If you add that up, it will take about 180 million years for Mars to be out of position by one inch (2.5 cm)," Rayman said. "We appreciate Mars making that sacrifice so Dawn can conduct its exciting mission of discovery in the asteroid belt."
The things we humans can do.


Blogger PeteY said...

I recall when Spirit had only just started driving about, that there was a photo that looked exactly like a muddy rut, one of its wheel tracks. There was speculation at the time that this muddy look could be caused by very salty brine in the immediate subsurface, but nobody took that idea seriously afaik.

I guess it would be pretty embarrassing if more than one lander had been operating in wet conditions and no-one had noticed.

February 20, 2009 1:47 am  
Blogger Paul McAuley said...

Extraordinary claims need extraordinarily strong evidence to back them up - and I don't think any of this is strong enough, yet. But to be in a position where scientists are hypothesising about liquid water right on the surface is pretty thrilling...

February 20, 2009 10:00 am  
Blogger PeteY said...

Well, yes, of course, but this one would be so easy to test conclusively - just touch the droplet and film what happens. Break the surface tension and it trickles down the leg. A couple of astronauts could sort it out in 30 seconds. But no doubt it'll remain hypothetical for 20 years until we get another chance with a robot. I'm a big fan of robotic exploration but it's all so frustratingly slow.

February 20, 2009 7:41 pm  
Blogger Paul McAuley said...

I'm a big fan of the robots too - especially Cassini and the two brave little toasters (one of which has found and touched evidence for hot springs. But yeah, it would be fantastic if an astronaut could kick into the side of a crater and get a gush of rusty muck all over his boot (I'm thinking of Spring Lane, close to where I went to primary school, where you could do just that, because it cut through the exact level where limestone met clay).

February 20, 2009 8:59 pm  
Blogger PeteY said...

Stroud, right? Is Spring Lane still like that? It sounds like a Jurassic deposit (you said some kids unearthed a big ammonite when you were young). Are there any good fossil hunting sites around there?

February 21, 2009 1:50 am  
Blogger Paul McAuley said...

Spring Lane was still trickling away when I last visited, a few years back. It's close by Selsley Common, which is where the ammonite was unearthed. There are several old quarries, all good sites for finding stuff. Although as it's now an Site of Special Scientific Interest and a designated Area of Outstanding Natural Beauty, I don't recommend in any way removing stones, let alone going in with pick and shovel. Most of the Cotswolds is oolitic limestone, formed under shallow seas and full of shelly material. One of the best way for finding larger fossils, back in the day, was walking the edges of fields after they'd been freshly ploughed. My fossil collection, such as it was, disappeared years back, apart from one, which I picked up from the side of a road - a Gryphaea oyster, commonly known as a Devil's toenail.

February 21, 2009 12:46 pm  
Blogger PeteY said...

Thanks for the tips, Paul. I'll put Stroud on my list of places to visit if I can ever drag myself away from Lyme Bay.

February 21, 2009 7:29 pm  

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