Archive of this excellent overview of past explorations of Mars and the future planned missions is posted at http://livestre.am/zo6Z . Lead page on the National Air & Space Museum website about this broadcast is linked to here. Go there if the livestream spot has been moved.
The top experts and chief scientists on Mars missions told about what has been found on Mars in the past ten years and what we're going to be looking for in the future. There was also Q/A with the audience that was also very enlightening.
Here are the notes I wrote during the broadcast. They are the things I found particularly interesting for my teaching but they are not definitely not a summary of what all was said. You'll need to see the broadcast for all the key points! I have notes for the first and last panels.
Jack Mustard told about the three basic climate periods of Mars:
Mustard showed a picture of a small section of Jezero Crater as seen by MRO from the press release of July 16, 2008 that is one of the river deltas that formed in the lake that was in Jezero Crater (I've used this in my lectures for several semesters now---image below). Clays and carbonates are found in the delta material and these are the types of sediments that would have been able to capture evidence of past life.
(For some reason, you can't find this image on the MRO site or the Photojournal site or the Mars Exploration Program site!)
In describing Mars' very dry conditions, Steve Squyres said that if you froze out all of the water vapor in Mars' atmosphere it would make a layer only 0.01 millimeter thick.
Regarding Gusev Crater, Squyres said that the crater floor (very likely) has sediments from Mars' wet period that were then buried by lava. Columbia Hills are islands of that sedimentary layer that stick up above the lava layer. From the Columbia Hills rocks, Spirit found chemical evidence of past hydrothermal activity (hot springs---water in contact with lava). Spirit also found patches of concentrated silica that would have been formed when water was in contact with lava like in fumeroles---could microbes have lived there?? Spirit found magnesium and ferric carbonates which means that water was present and the chemistry would have been suitable for life in the past.
The main reason for choosing Opportunity's landing spot in Meridiani Planum was that orbit images showed a large amount of hematite in that area. Hematite is a mineral that forms in the presence of water. The rocks there are made (partly) of sulfate salts. When Earth sea water evaporates, you get those salts too. The Mars Exploration Rovers are not the first ones to discover water---Mariner 9 did that way back in the 70s with the polar ice caps. The rovers have added a detailed (and significant) layer to the water story of Mars. Any water on Mars is now in the form of sulfuric acid---not a pleasant place for life now.
Squyres hopes that Opportunity will get to Endeavour before Curiosity lands in August 2012. The crater rim material of Endeavour has clays and in the spirit of friendly competition he wants his rover to make detailed analysis of the clays before Curiosity.
When asked how deep we would have to dig to find present (extant) life, Squyres estimated 1 to 2 meters so that it was shielded from the cosmic rays that hit the surface (Mars has no magnetic field and too thin an atmosphere to shield its surface from even low-energy cosmic rays).
Could we use the water below Mars' surface for future missions and "live off the land"? Yes, but the problem is the energy required to access it and use of electrolysis so we could use it for rocket propellant.
Mustard noted that although Mars' rotation axis is now tilted by about the same amount as the Earth's, about 100,000 years to up to 5 million years ago, the rotation axis was tilted about 45 degrees. Would that have made Mars warm enough for life? (See also the obliquity image from the Mars Phoenix site.)
The biggest unknown of the water question is WHEN did it flow?
Panel 2 note: Mars Express (ESA) is exploring the water cycle on Mars. How the subsurface water is transported to the surface, then to the atmosphere, and finally escapes to space.
Mary Voytek five characteristics or needs of life (just the thing for my astrobiology class)
The system as a whole can respond to Darwinian evolution which allows a great diversification of life (as well as enable it to adapt to a change in the environment---Mars and Earth have certainly undergone great changes in their environments!).
Voytek made a plug for the book "The Limits of Organic Life in Planetary Systems" from the National Academies Press. (You can download a PDF of the book for free.) Published in 2007 and even back then we knew that the life can live in a w-i-d-e variety of environments. We have to be careful of not being too focused on what type of life to look for. For instance, there could be life using liquid methane (like that on Titan) as its solvent, instead of water.
John A. Grant is the head guy of the group that is determining where Curiosity (Mars Science Laboratory) will land. Constraints on landing sites are that the elevation must be no higher than 0 kilometers (I think that's so that the atmosphere is thick enough (?)) and the location will be close enough to the equator (within 30 deg N and 30 deg S) to stay warm enough. Eberswalde Crater (has a river delta feature), Gale Crater, Holden Crater, are the Mawrth Valley are the top four contenders. All would be excellent sites---select the link to find out more about these sites. (Will need to choose within the next few months since MSL launches in November 2011).
When asked by an audience member if we'd send experiments like the labeled-release experiment on Viking in future missions, Voytek said no. That is because experiments like Viking were so specific to particular forms of life. We now know that life can be much different than life on Earth (and certainly much different than what people thought in the 1970s, when Viking was constructed). We need to be careful of sending experiments that are not so specific that we overlook life happening all around the lander/rover.
Jennifer Eigenbrode talked about the experiments on MSL to detect organic molecules on Mars. One way to verify that a martian sample is not contaminated by Earth organics is that before each martian sample is loaded into its chemistry lab, a sample will be taken out of an absolutely pure brick on MSL that has been "scrubbed" of any organics from Earth so that MSL will have an always updated "background" organics signal to which to compare the martian sample against. If we find organics, will the MSL experiments be able to distinguish organics formed by biological processes from those formed without life? (Link to how ESA's ExoMars Rover will look for biological processes.)
She showed an image from the gallery at Space4case---a lot of nice rendering of Mars present and past there.
In response to a question from the audience about the microbes found in Mono Lake that use arsenic, Voytek noted that the microbes are still carbon-based. They are able to use arsenic in place of phosphorus. Arsenic is right below Phosphorus in the periodic table so it has similar chemistry (valence electrons) to Phosphorus.
Well, those are my notes. Certainly, a lot more covered in the two hours. What important things did you note?
last updated: January 16, 2011