Water on Mars!

Just after I write a blog on “The Martian”, NASA announces evidence for flowing water on Mars. Yes, the announcement probably was to spark some interest in NASA from the film Matt Damon is going to star in. The evidence seems to depend (and I have yet to see the relevant scientific papers) on some gullies carved in the side of one crater that grow when the temperatures are higher, and these gullies are best described in terms of water flow. The temperature of Mars is below the freezing point of water, and the air pressure is about half that needed for liquid water to exist, so how can this be? Where did this water come from?
There are various theories, one of them being there are underground aquifers where water flows, and these come to the surface. On a personal level, I cannot see this as being likely. An underground aquifer would still need heat to melt the water, and while there might be geochemical heat, why is this heat around craters? Actually, there are a number of craters on Mars that show signs of ancient water flow, and the usual explanation for these is that when the impact occurred, the heat of the impact melted any ice that was around, and this water was available to emerge from time to time, until it froze again. Various calculations suggest liquid water could be available from such impact heating for up to 50,000 years. However, if this were a new crater, and I understand it is not, we would still expect the water to emerge from anywhere along the side or bottom of the crater, and not specifically from near the top.
The most likely explanation I can come up with is that the water comes from the atmosphere. Actually, the atmosphere is quite humid; about 50%, and every now and again we even see cirrus clouds on Mars. The basic problem is that there is not very much air anyway. But, back to the question, how does water flow on Mars?
First, if you dissolve something else in water, the melting point is lowered, so this water is almost certainly a strong solution of something in water. Further, if you dissolve something in water, the boiling point is raised, or alternatively, the vapour pressure is lowered, by an amount dependent on how much solid is in the water. This is likely to be part of the answer, because there appears to be one new piece of information in the announcement. The gullies are not new, nor is the argument that they are caused by water flow, and I had references to that in my survey of information in Planetary Formation and Biogenesis, which was published as an ebook some years ago. No, what is new here is that there is spectral evidence for perchlorates in the bottom of the crater.
What seems to happen on Mars is that chlorides, which are rather common if water can concentrate them (the sea has quite a bit of sodium chloride), are oxidized, thanks to the hard ultraviolet radiation, to perchlorates. Magnesium perchlorate is deliquescent, that is, it sucks water out of the atmosphere and dissolves itself in it, and the melting point of the solutions will be quite lower. I don’t know what it would be, but calcium chloride, which is also deliquescent, when mixed with ice, melts the ice and lowers the temperatures to about minus 40 degrees. Magnesium perchlorate would probably do something similar.
What does that mean for life on Mars? As far as I am concerned, there is no change, and it might have got harder, the reason being that perchlorates are strong oxidizing agents, and may well interfere with certain life functions. Further, the solutions are saltier than “The Dead Sea”, and as the name suggests, it is not brimming with life.
This method of getting fluid water might also be thought to solve the problem of how to “make water” in the book, and presumably the film, “The Martian”. All you have to do is to distill off the water, then reuse the perchlorate. My personal view is this would be far too slow, and to get water, in my novel Red Gold I suggested simply pumping up the air pressure and squeezing/chilling the water out. Even better is finding ice, although that might be easier said than done in an emergency. So, while this announcement really makes little difference to the likelihood of finding life on Mars, it does make the chances of settling on Mars and surviving a little better.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s