Tuesday, October 10, 2006

What's the deal with water on Mars?

So here's a comment I got today: "I followed the reports early on that there was some impressive evidence that Mars was once covered with water. However I also seem to recall that a few months later there were some dissenting view points. So, riddle me this science girl...What is the deal? Was Mars a wet and wild world of acidic, sulfur laden dihygrogen monoxide? Are there suspected sites where drilling might reach liquid water? Or is Mars just a dusty bin of chilly rocks?" OK, so here's Science Girl's attempt to summarize many people's work on this topic!

I think the consensus now is that there is a lot of evidence of liquid water in Mars' past, but we're still a little fuzzy on the exact details - when, how much, how long it lasted, and where it was. Orbital photos have long showed things that look like branching river valleys and more recently, the MOC camera has captured many images of gullies in craters that might be caused by seeping subsurface water. There's definitely ice in the subsurface now, and presumably if you dug or drilled, you'd be able to get to it - the Phoenix mission will try to do just this - but it's likely to be mixed with rock or dust like the Arctic tundra, not like a subsurface glacier.

One of the biggest contributions to the story is Opportunity's view of the rocks at Meridiani Planum. There's pretty convincing evidence that these rocks are sediments that were laid down by flowing water on the surface. But, the environment that formed the rocks is probably more analogous to a braided stream or wash in the desert southwest than the oceanic shelf off the East Coast. We don't know exactly when these rocks were made, but we do know that at that time, there was a lot of sulfur and oxygen at the surface, making the Martian environment pretty harsh, acidic and oxidizing - very unpleasant for life as we unerstand it. We're just now trying to come to more understanding of the acidic/sulfuric environments vs more "clement" environments with CRISM, a mapping spectrometer on the MRO orbiter, which will be able to pick out areas with sulfates (acidic, sulfurous weathering) and areas with things like clays that we think formed under more neutral and less sulfurous conditions.

But having said all that, remember that Mars is an entire planet. Think about it - is the Earth covered with water? Well, yes and no, sometimes it was in some places and sometimes in others, sometimes the water is liquid and sometimes it is ice. The rocks exposed in the Grand Canyon were laid down by a vast ocean 500 million years ago, but southern Utah is now a windy, barren desert. Underneath the Pacific Ocean, the rocks are formed by erupting magma and have only trace amounts of water in them. The Earth is geologically complex and has 4.5 billion years of history complicating it, but we've been living here and studying the world around us for tens of thousands of years. Mars is also geologically complex and also has 4.5 billion years of history, but we've been studying it only remotely and for only three decades. It's a long process, figuring out Mars, and science is about getting more and more little pieces that we integrate into our understanding, rather than sending one spacecraft and expecting it to tell us the conclusive story. But, of course, each of our little pieces comes with a price tag and so we need to make sure we wring all the science we can out of it and tell everyone what pieces we are finding!


the dude in the back said...

Nice answer, thank you for taking the time. I haven't read much about the Phoenix mission so your link was helpful. Having read about it (Phoenix) I am kind of bummed. You would think that with a cool name like, “The Phoenix Mission” that they could put some horse power in that bad boy. Can you say, A-CAERDDCOIPHE? (Autonomous-Compressed Atmosphere, Extreme Rotary Drilling Device Capable of Interplanetary Hydrogeological Exploration).

Okay, sure, I made A-CAERDDCOIPHE up, but you get my point. I mean they need some more motor heads over there. It is just that the little back hoe thing looks sort of light weight, as in sickly and not up for the job. I’d like to see some real wells drilled out there, some dust slinging, rock chewing, one hundred footers. That would be impressive. Perhaps you might consider chatting with your fellow big brain types about that. No doubt your soon to be found fame as “Science Girl” with the oh so clever catch phrase, “Riddle me this Science Girl…” will catapult you to ratings way higher than that Bill Nye guy. I predict that these ratings will give you the political capital you will need to influence a multi million, if not billion, dollar project like Phoenix.

By the way, you do realize that if you get a syndication deal under the name "Science Girl", I will expect some sort of compensation. And none of those tricky chess playing, “I can’t even begin to think as slow as you” big brain tricks either. I want some meaningful compensation, like rover swag or something. (In the likely event that you are the wholesome type, unfamiliar with the meaning of the word, “swag”, here is the definition.

Swag: Slang meaning difficult to obtain stolen merchandize (DTOSM), recently bastardized by the marketing types and The Man, now it could mean just about anything including, but not limited to, over priced, caffeinated, triple filtered, ultra-natural spring water. (For the record, I like my swag to be more inline with the first definition.)

Anyway, the lame acronyms have been sanitized for your protection and were specially designed to make you feel more at home. Thanks again for the answer.


Are you SURE those gullies were formed by liquid water? ... Just checking..

Anonymous said...

Nicely summarized, Barb. No wonder you get all those media types wanting you for their articles/programs!! I particularly like the examples for illustrating the complexity of the Earth's water story.
Oh, and yeah, that HiRes picture (below) is one of the coolest shots of Mars ever. With that kind of resolution now (12 in/pixel!!), those little green (red?) guys better be watchin' the skies or we'll catch 'em on camera!

Tim said...

I stumbled across your blog and have found it very interesting.
You said:
"But, of course, each of our little pieces comes with a price tag and so we need to make sure we wring all the science we can out of it and tell everyone what pieces we are finding!"

You are right! So why is it that NASA is sending up another rover that will do nothing but scratch the surface? This is a waste of money and time, that could have been spent on a much better machine that could drill to two, three, even four hundred feet, collecting core samples, storing them, with possible return to Earth.

I have been drilling water wells for over thirty years. NASA could have built a drilling machine running four to six high powered, high torque, low speed, electric motors, powered by a nuclear battery, similar to the moon lander. The battery would provide more than enough power for many years to come. You could then drill thousands of test holes to any depth that you want. The holes could be as small as one inch to as large as four inch in diameter.

The samples could then be set aside for retrieval by another mission. They could also be scanned, examined, photographed, cut, diced, sliced, minced, chopped, etc... You would have a better sample because it is a core sample, and not "top-soil" mixed with everything else.
With a "nuke battery" you could run this machine for 20 years or more, limited only by weather and the durability of the bit.

I think that "the dude in the back" had it right when he / she said "I mean they need some more motor heads over there. It is just that the little back hoe thing looks sort of light weight, as in sickly and not up for the job. I’d like to see some real wells drilled out there, some dust slinging, rock chewing, one hundred footers. That would be impressive."

Yes indeed!!

NASA needs to start really doing something spectacular to capture the imagination of the world or its funding will dry up; just like Mars did. That is if there really was any water there to begin with. Just imagine drilling a well and finding water or ice four hundred or so feet down; proof positive that Mars once was a liquid planet.

Great blog!

samantha said...

It's posts like this one that make me realize why I love science all over again. My studies and research have focused on earthly environments, but I love learning about more. Fascinating stuff! ...not to mention the witty comments supplied by the Dude in the Back. It all makes for such an intersting read.
I agree with him on the Science Girl part. I see it starting off as on online answer thing, moving along to televison, then to comic books and movies. I would partner up with Dude though...a side-kick type deal; a goofy, yet adorable assistant. It's the scientific formula for celestial success!