Tuesday, February 17, 2009

Valley Networks formed by basal melting

Well just to show that my wildest imaginings are indeed backed up by scholarly research -- here is an article by Michael Carr (2003) about:

Basal melting of snow on early Mars: A possible origin of some valley networks

He writes that:
The perception of an early, warm Mars is, however, being increasingly questioned because of (1) failure to detect weathering products from orbit [Christensen, et al., 2001], (2) the vulnerability of an early atmosphere to losses by impact erosion [Melosh and Vickery, 1989], (3) the likely rapid scavenging of CO2 from the atmosphere by weathering under warm, wet conditions Pollack et al., 1987], and (4) climate modeling studies which show that it is difficult, if not impossible, to sufficiently warm Mars with a CO2-H2O greenhouse so that rainfall could occur [Haberle, 1998; Kasting, 1991]. The latter problem is particularly acute early in the planet’s history, when the Sun’s output was likely significantly less than it is today [Newman and Rood, 1987].

There is a lot here about how the thermal physics could create melted ice water, but very little about the morphology of the valley networks and whether they are consistent with this type of formation. Is anyone familiar with more work done on this hypothesis?

Monday, February 16, 2009

Biere De Mars...

Well, ever on top of the exciting intersection between beer and Mars, I'm happy to report that Biere de Mars will be back and perhaps with a new recipe. The old label is pictured to the left here, with the new label below.

Turns out -- you learn something new every day -- that Mars really means March. So while they played the Mars planet card in their old label, the new label doesn't look so martian.

I look forward to tasting the new beer.

Mars Explained... I think.

I just had a paper come out in Nature Geoscience about the sediments at Meridiani Planum -- please go and see it. The abstract is the following:

The sulphate-rich deposits at Meridiani Planum, Mars, discovered by the rover Opportunity, were proposed to be playa evaporites that had been reworked by eolian processes. Alternative hypotheses include volcanic or impact-driven formation of the sediments. Here we argue that the cation chemistry, scale, mineralogy and structure of the Meridiani sedimentary deposits are best explained by eolian or impact-driven reworking of the sublimation residue from a large-scale deposit consisting of dust and ice. We suggest that silicate material underwent significant acid weathering inside the ice deposit when thin films of water, formed through radiant heating, enabled the reaction between silicate material and sulphate-rich aerosols deposited from the atmosphere. The massive ice deposit could have formed during a period of high obliquity or polar wander, and subsequently sublimed away when obliquity changed or the pole moved to a new location. We propose acid weathering inside massive ice deposits as an explanation for the formation of many of the sulphate-rich layered deposits on Mars, which share many characteristics, including mineralogy, structure, erosional characteristics and size, with the sediments found at Meridiani Planum.

So with that introduction, my grand unified theory of Mars, at the risk of coming out half-baked or maybe even a quarter-baked:
  1. In the first couple hundred million years of Mars' history (perhaps shorter) conditions on Mars were probably very different from today, the planet had just accreted, I imagine there was a fair amount of chaos. The question is whether or not this period featured any significant aqueous alteration that we can see today. This hinges on whether or not significant water was present on the surface, and not boiled away by impacts, volcanism, or just not degassed from the interior yet. I'm going to posit that the extensive phyllosilicates detected in ancient crustal rocks are from this period -- but I've got another couple of possibilities later on.
  2. As things calmed (and cooled) down the next question is whether there was a thick atmosphere -- and how long it lasted. My argument is that if there was a thick atmosphere it was not long lived (not more than 100 million years or so), it was lost to space through impact events, stripping by solar wind, etc.. My reasons for thinking this are that we don't see well developed fluvial features, I don't think evidence for an ocean is strong, there are not extensive carbonates or other evaporite deposits from this period we've found (Please read above for Meridiani).
  3. I think Meridiani is really the key for understanding the conditions during this period. Most important in my mind are the constraints posed by the chemistry and mineralogy. We've got a deposit of silicates that have been completely altered by aqueous alteration but show no fractionation in cation composition from a basalt. This indicates that it was weathered in a closed system -- a low-water-rock ratios.
  4. So we've got a planet where there are fluvial features, ice deposits, and the like, which all require some sort of recharge. But we don't have enough CO2 to account for a warmer climate and rainfall. Instead we have a planet which undergoes huge obliquity variations through time which serve to redistribute the ice from the poles to the equator. This could be the recharge mechanism we are looking for. And if this ice-weathering idea proves to be feasible, we can explain sulfate formation as well.
  5. Outflow channels -- require huge volumes of water, repeated surges. But their source regions aren't large basins with many tributaries leading into them -- they are just relatively small chaos terrain. So we have giant channels that require massive floods but no obvious source that's big enough. Ice seems to meet this requirement as it would sit on the surface and provide a massive source -- it also has the tendency of creating large floods.
  6. Layered Terrain -- This includes interior layered deposits (ILD's), crater mounds, as well as plains deposits (meridiani-type). The idea here (not original of course) is that layered terrain closely resembles polar layered deposits and formed from the same mechanism. It is though polar layered deposits are a result of obliquity variations. One issue is reworking - and this is what needs work - some of these deposits would preserve their original layering -- even though ice has sublimed away (perhaps ice still exists in the cores of these ILD's and crater mounds?), others would be reworked by aeolian, impact, and fluvial processes. Can we tell the difference?
  7. Valley networks -- Might be related to basal melting of obliquity ice deposits. I find it interesting that they are generally located on an equatorial band.

I think that pretty much captures it for water on Mars. Comments anyone?

Update: Check out the article at space.com

Tuesday, February 10, 2009

Mars Explained..

Well my Nature Geoscience paper is going to published Feb 15, as an advance online publication. I don't think it will be journalified until March. But it will be out there on Feb 15 -- so look for it. I think it is still under embargo, so I'll just wait for that so I don't get in trouble. All 4 readers of this blog might still be too much, but I figure it'll be a big release on that day. So after that I'll

Monday, February 2, 2009

Why should we go into space?

Ok, well this is a big question I'll be coming back to, mostly to refine the ideas I'm putting out right now. But this is something I wrote as input to the Space Studies Board of the National Academies. They were asking for public input for their "Rationale and Goals of the US Civil Space Program". Deadline was Jan 30th, so sorry folks, I should've started blogging earlier. Here's the website in case you are interested.

Anyhow this is what I wrote:

The civil space program's goal should be to increase opportunities for the citizens of both the United States and the World. In the most general sense, opportunities are situations where new knowledge, new infrastructure, or new technology opens a door to someone that had previously been closed. This can include inspiring and motivating someone to achieve, uncovering key knowledge that advances the scientific endeavor, or making a discovery that allows for new entrepreneurial activity. New opportunities in the space program are created through scientific investigations and human exploration. While many activities can be characterized as increasing the opportunities for the American people, much thought should be given to which activities maximize the potential opportunities in space.

In order for the civil space program to truly make important contributions to the opportunities available to the citizens of the country and the world, it should focus on enabling entrepreneurial activity, building transportation infrastructure, exploring the nearest planetary bodies to the Earth in search of resources useful to human civilization (primarily H2O), and exploring the solar system for pure scientific discovery.

Viewed with the lens of opportunity, endeavors such as the space shuttle, space station, and planned lunar outpost are extraordinarily inefficient for achieving what could have been achieved since none of these things enable future activities and become ends in and of themselves. If permanent hardware must be placed in space, lets make sure that it can help leverage future endeavors.

Entrepreneurial activity is of course a highly desired goal for space exploration as it provides a means for powering opportunity growth. However, many people see entrepreneurial activity as a means for achieving their desired ends (colonies in space, people living on Mars, etc.) and thus think about it in a limited way. Prizes are a good example of this where the hope is that entrepreneurial activity can be harnessed to achieve symbolic goals. This is an inefficient mechanism because the goal being set may not be the best way to spark entrepreneurial activity. Entrepreneurial activity should instead be seen as the goal itself, whatever form it may take. The civil space program should take advantage of open competitions for their limited transportation resources, in order to find the best ideas available.

Exploration for resources in near Earth space should be viewed as a primary goal of the space program. The availability of water that can be easily accessed greatly enhances the possibilities for what humans can accomplish in space. A giant hurdle for any space venture is our lack of knowledge of nearby planetary bodies. Water (H2O) should be seen as the most important resource to search for as it provides use in many different ways (rocket fuel, human sustenance, etc.). Water is also a good thing to look for because we have a high probability of locating large amounts of it in near earth asteroids. Looking for water on the Moon using ISRU is like going to the Sahara to look for water when you could have just as easily gone to the Pacific ocean.

Scientific discovery is also an incredible driver for opportunity growth. The more that is learned about ourselves, and the solar system around us, the more opportunities we can uncover. Science also dovetails with exploration as it provides the how and why for things that are discovered.

Sunday, February 1, 2009

Drinking Beer on Mars

See if you can pick out Leslie Nielson in this video...