Archive for the ‘Phoenix’ category

Jaded by Mars Organics

September 11, 2010

So, you may have heard the news making the rounds last week that a new analysis of the Viking data suggests there may actually be organics and (dare I even say it?) life on mars! Yawn. Consider me underwhelmed.

The gist of the story is this: A long-standing mystery in Mars science has been why the Viking instruments were unable to detect any organic molecules on Mars, not even at a level that would put Mars on par with the moon. Now, 30 years later, the Phoenix lander discovered the perchlorate molecule in the arctic martian soil. Perchlorate is a powerful oxidizer, and by heating a soil sample containing organics and perchlorate, you’re bound to destroy the organics. So, if there were perchlorates at the Viking site, then maybe the Viking instruments destroyed the very organics they were trying to find! The few traces of organic compounds detected by Viking were interpreted as residue from the chemicals used to clean the instrument, but the new results show that organics oxidized by perchlorate can also form those compounds.

To me, this sounds pretty familiar. See, as I understand it, the leading theory for what happened to the organics on Mars to bring them to levels below the moon is that some unknown oxidizing agent had destroyed the organics. So, now we know what the oxidizing agent might be, but it seems that the prevailing theory still holds. I suppose the excitement comes from the possibility that the organics could remain intact until the soil is heated, and so low-temperature investigations might detect them. But the modeling in the paper did not consider that the organics were sitting at the Martian surface for perhaps billions of years. Yes, heating in the oven might destroy the organics, but that may be meaningless if they were all broken down millions of years ago by UV radiation. As for the traces of organics that Viking did detect, as the press release mentions, they had the same Cl isotope ratio as Earth. Now, it’s not impossible that Mars has the same ratio as Earth, but it would be a coincidence. Invoking coincidences in science makes me uncomfortable.

A few years back, during my summer internship at NASA Academy, I earned the nickname “aguafiestas” which translates to “that guy who ruins all our fun”.  I earned the nickname for debunking some internet hoax emails that my friends were sending around, but it’s a nickname I wear proudly.

So, maybe I’m being an aguafiestas again with this press release, but I just can’t get that excited about the announcement. I will say that I am really looking forward to the results from the SAM instrument on MSL, which should be powerful enough to detect organics wherever they are hiding on the Martian surface. I’m not naive enough to claim that it will answer all our questions, but it might. Even an aguafiestas can hope!

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New Photos of Stuff on Other Worlds

October 29, 2009

I always make the mistake when on vacation of taking too many pictures of scenery and not enough pictures of people. Years down the road, the most interesting photos are not landscapes, but the ones that we can look at and say “I remember when we did that!”. And that’s why I think it’s great that we now have cameras around the Moon and Mars that can do the same. LROC at the moon has been able to take some spectacular photos of the Apollo landing sites, including a new one shown below. HiRISE at Mars has been able to take photos of the Mars rovers, Viking landers, and more recently the Phoenix lander.

Phoenix went silent as northern Martian winter crept in, covering it with CO2 frost, but the latest HiRISE image, taken in the spring, shows an ice-free Phoenix! It probably won’t wake up again, but it’s good to see our lander again. The spring images are somewhat grainy because the sun had just peeked above the horizon and light levels were very low. Emily Lakdawalla has a post with more information about this and other HiRISE images of Phoenix.

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Credit: NASA / JPL / UA / animation by Emily Lakdawalla

If it’s fun to see our robots again, it’s even cooler to see evidence of humans landing on the moon. Now that LRO is in its final orbit around the moon, it is returning some really excellent photos of the Apollo landing sites, including this new one of the Apollo 17 site. You can even see the flag! For more information and closer views, check out the LROC site.

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This high-resolution view of the Apollo 17 landing site shows details as small as the flag! Click to go to the LROC site for higher-resolution versions.

LPSC 2009: Day 1

March 24, 2009

Unfortunately I missed the earliest sessions today because I had to drive down to Johnson Space Center to get a badge. I am going to be working there for four weeks after LPSC and another five weeks later in the summer, characterizing rock samples and shooting them with a laser, so I needed a badge to be able to do that work. I got back to the conference just in time for Bill Boynton’s talk about the evidence for Carbonates at the Phoenix landing site.

He presented results from TEGA, the Thermal Evolved Gas Analyzer, which is a set of 8 ovens that are used to heat a sample up to ~1000 degrees C and analyze the gases that are created. When compounds undergo a phase change, they tend to absorb energy without increasing in temperature. Think of ice in a glass of icewater; the system doesn’t start warming up until the last bit of ice has melted. Until that point, any additional energy goes toward the phase change between solid and liquid rather than warming up the mixture. TEGA operates on the same principle: by calculating how much energy is required to heat a sample it can detect phase changes. It also sends any gases created during heating to a Gas Chromatograph Mass Spectrometer to be analyzed.

Phoenix found evidence for carbonates, likely formed in the presence of liquid water, in the soil of the Martian arctic.

Phoenix found evidence for carbonates, likely formed in the presence of liquid water, in the soil of the Martian arctic.

During analysis, there was a significant release of carbon dioxide at high temperatures, indicating the decomposition of calcium carbonate (the same material that makes up limestone on Earth). Calculations show that if the carbonate was formed purely due to atmospheric humidity, it would be much less than 1% of the soil, but the TEGA results require something like 3%-5%, indicating that the carbonates formed in water.

Another interesting talk was from Delphine Nna Muondo, who talked about the use of laser pulses to simulate impact shocks. I will be using pulsed lasers for my upcoming research so it was interesting to see how another research group is using the same type of laser for very different purposes. Their work was focused on determining the chemistry induced by impacts, which they simulated with laser pulses. Laser pulses have the advantage over high-speed gun experiments that the can deliver energy equivalent to 100 km/s impacts, much higher than what can be achieved with actual impactors. Also, laser pulses are easily repeatable, and there is no contamination of the target by the impactor. The disadvantages of using lasers to simulate impacts are that natural impacts have longer-lasting shock waves, and they couple their energy to the target differently. Nonetheless, Muondo showed that laser pulses do induce some chemistry, which may explain the presence of some organics in the outer solar system.

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Laser pulses can be used to simulate extremely high velocity impacts.

Later in the day, one of the most interesting talks was one from Nilton Renno, discussing the possibility of liquid H2O at the Phoenix lander site. He suggested that the odd growths observed on the lander’s leg may have been extremely salty water droplets. Salts are very common on Mars and Phoenix showed that the soil was rich in perchlorates, which can lower the freezing point of water down to -75 degrees C. He suggested that daily variations in surface temperature, which oscillate above and below -57 C, would cause a layer of very salty water to be concentrated just beneath the surface. During landing, Phoenix’s rockets blasted through the soil and uncovered ice, and in the process “splashed” this brine onto the lander’s legs. The uncovered ice began to sublimate, and the water vapor then was absorbed by the concentrated brine droplets, causing them to grow! The growth slowed down toward the end of the mission because the exposed ice was no longer sublimating and providing water vapor.

Putative droplets of brine growing on Phoenixs leg.

Putative droplets of brine growing on Phoenix's leg.

The talk was pretty similar to one which I reported on back in December at AGU. I am of pretty much the same opinion; that it sounds like a plausible argument to me, but that it may not be as compelling as Renno thinks since the Phoenix team hasn’t been shouting this result from the rooftops.

New Google Mars

February 2, 2009

Google Earth’s latest edition was just released and guess what? It has a Mars setting! There was a way to overlay Mars data on the Earth globe in previous versions, but now that’s no longer necessary: just click a button and you’re on Mars. You can choose from a variety of global maps including topography, Viking images, Day and nighttime infrared, and visible color. It also has footprints for high resolution cameras like HiRISE, CTX, MOC, CRISM, and HRSC, with links to the full-resolution images. And most exciting, it has 3D topography! Now you can fly around in Valles Marineris or check out the view from Olympus mons.

The view from the edge of the Olympus Mons caldera in Google Mars.

The view from the edge of the Olympus Mons caldera in Google Mars.

Olympus Mons dominates the horizon in this Google Mars view.

Olympus Mons dominates the horizon in this Google Mars view.

Another way-cool feature is the ability to zoom into panoramas taken by rovers and landers, as shown here for Opportunity.

The Opportunity rover's traverse. Each camera icon is a panorama that you can zoom into.

The Opportunity rover's traverse. Each camera icon is a panorama that you can zoom into.

Part of the Rub al-Khali panorama taken by the opportunity rover.

Part of the Rub al-Khali panorama taken by the opportunity rover.

And finally, you can load selected Context Camera images right onto the globe, to take a high-res look at areas of interest, such as the Olympia Fossae troughs shown here. I don’t know what’ you’re waiting for: go download the program and try this out for yourself!

CTX image of the Olympia Fossae troughs.

CTX image of the Olympia Fossae troughs.

AGU Day 1: Phoenix

December 16, 2008

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This AGU is the first major meeting since Phoenix died last month, and so everyone has been eagerly looking forward to hearing about the results now that the team can focus on science instead of operations. Emily has posted a nice  summary of her notes from the Phoenix sessions, so go take a look and then come back here for what I thought were the highlights.

The results presented today were very preliminary, and everyone who gave a presentation emphasized that there’s still a lot to do, especially in interpreting the chemistry data. Now that they have the data, they will be trying to duplicate the observations using an identical set up on earth.

One of the most interesting things to me was the discussion of perchlorates. I know they were big news back when they were first discovered, but Mike Hecht gave a good explanation of their properties and implications that cleared things up for me. Perchlorates are found on earth in very arid environments like the Atacama desert in Chile, and are measured in grams per hectare. For comparison, at the Phoenix landing site, Hecht said that it would only take a few handfuls of martian soil to get a gram of perchlorate.

The perchlorate ion.

The perchlorate ion.

Perchlorates are extremely soluble in water, and act as a great antifreeze, making brines with low melting points (-70 C). They also are quite reactive, and when heated they give off oxygen and heat. Hecht said that there is so much perchlorate, and that it is so soluble and reactive with water, that it is possible that perchlorate controls the water cycle on Mars. I also thought it was interesting (if disappointing) that perchlorate ruined the chances of finding any organics: when you heat it up it releases oxygen, which would react with any organic molecules in the soil and burn them up. It seems that Mars is still stubbornly hiding its organics from us.

Another aspect of perchlorate that I thought was interesting is that it is used as an oxidizer for rocket fuel, since it gives off oxygen when heated. This makes it a potential resource for future Mars missions: astronauts could manufacture their own oxygen just by cooking the soil, and could have a ready-made oxidizer for the return trip.

One of the other talks that I thought was especially interesting was Mike Mellon’s discussion of the polygonal terrain near the landing site. He showed that the ice in the soil, which was generally at ~5cm depth, is mostly in equilibrium with the atmosphere. In other words, it was right where we expected it to be. He also pointed out that there are several different scales of polygons visible from orbit and from the surface. The size of polygons in a periglacial landscape is determined by the depth of the ice table, which is affected by climate. So, the fact that multiple sized polygons are visible means the climate has changed since the surface formed, sometime in the last half-billion years or so.

Polygonal terrain as seen by Phoenix.

Polygonal terrain as seen by Phoenix.

Finally, the last talk was by far the most controversial and interesting. Nilton Renno discussed what he believes is evidence of liquid water in the soil. He pointed out that an abundant salt in the soil (such as perchlorate) would be expected to form thin brine layers during the same freeze-thaw cycles that form the patterned ground. During the landing, a few centimeters of soil were blasted out of the way by the rockets, and Renno thought that some brine droplets were deposited on the lander leg. He made the very reasonable obervation that the white spots on the lander leg grew over time, while ice on the ground disappeared by sublimation. If ice on the ground sublimates, you would expect that ice on the warmer lander leg would sublimate faster, not grow. Renno’s hypothesis is that brine droplets on the lander leg sucked up the water that sublimated from the ice on the ground, causing the observed growth. Later in the mission as it got colder, they stopped growing and sublimated away.

Could these growing blobs on Phoenix's leg be liquid water? Maybe.

Could these growing blobs on Phoenix's leg be liquid water? Maybe.

Unfortunately, Renno’s talk was the last one of the session, and everyone was so burned out that there weren’t any questions. I think he makes a very interesting argument, and it makes sense to me. There may be a simple explanation for why he is wrong, but I can’t think of it. Still, it strikes me as odd that nobody else has brought this up if it is as compelling as Renno seemed to think it was. Could Phoenix have found evidence of liquid water just centimeters below the surface? Maybe! I’m looking forward to seeing the community’s response to this possibility.

Phoenix Mission Over

November 10, 2008

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Well, it’s official. Phoenix is dead. JPL sent out a press release today announcing that after more than five months, they stopped hearing from the lander on Nov 2 and have been unable to re-establish contact. Although the mission is over, I’m sure that science results will continue to be announced as the team finally has time to sit down and really analyze the data. Here’s a quick summary from the press release of the mission’s science accomplishments:

Phoenix’s preliminary science accomplishments advance the goal of studying whether the Martian arctic environment has ever been favorable for microbes. Additional findings include documenting a mildly alkaline soil environment unlike any found by earlier Mars missions; finding small concentrations of salts that could be nutrients for life; discovering perchlorate salt, which has implications for ice and soil properties; and finding calcium carbonate, a marker of effects of liquid water.

Phoenix findings also support the goal of learning the history of water on Mars. These findings include excavating soil above the ice table, revealing at least two distinct types of ice deposits; observing snow descending from clouds; providing a mission-long weather record, with data on temperature, pressure, humidity and wind; observations of haze, clouds, frost and whirlwinds; and coordinating with NASA’s Mars Reconnaissance Orbiter to perform simultaneous ground and orbital observations of Martian weather.

Phoenix wrote a farewell note, to be published when the mission ended. Here’s an excerpt:

If you are reading this, then my mission is probably over.

This final entry is one that I asked be posted after my mission team announces they’ve lost contact with me. Today is that day and I must say good-bye, but I do it in triumph and not in grief.

As I’ve said before, there’s no other place I’d rather be than here. My mission lasted five months instead of three, and I’m content knowing that I worked hard and accomplished great things during that time. My work here is done, but I leave behind a legacy of images and data.

Phoenix Blogs!

November 6, 2008

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Now that the mission is winding down, the Phoenix lander had broken out of the confines of twittering and is writing a few longer blog entries over at Gizmodo!

Also, over at Wired, they have announced the winners of the Phoenix epitaph contest. The #1 choice was:

Veni, Vidi, Fodi (I came, I saw, I dug)