Monday, October 30, 2006


Spirit made it through Sol1K successfully! We have data products on the ground with the sol 1000 timestamp. But 1000 sols can really take its toll: Mars Rover Beginning to Hate Mars. Bruce Banerdt assures me that his comments “were taken completely out of context.”

To celebrate Sol1K, check out the awesome panoramas of Spirit's winter haven. If you have red-blue glasses, I highly recommend the red-blue anaglyph.

Red-blue-green: Why do some comet atmospheres glow green? The coma contains cyanogen (CN) and diatomic carbon (C2), which glow green when illuminated by sunlight (called "resonant fluorescence”) (from Science@NASA).

Bang, zoom, straight to the Moon

This week, the Committee for the Scientific Context for Exploration of the Moon had our third meeting. What we’re charged to do is to consider the science that can and should be done in the new Vision for Exploration at NASA, which begins with new missions, both robotic and human, to the Moon. In some ways, it’s an easy task, because we haven’t landed on the Moon in 35 years, so many of the scientific questions we had after Apollo are still outstanding. In other ways, it’s a difficult task, because our understanding of all the planets has evolved so much since then, and we need to reconsider how the Moon fits into the solar system and in what ways it is unique. The Moon’s combination of unique science and accessibility make it a really exciting place to talk about and I really enjoy being in a room full of 15 people all jazzed about the Moon!

Some of the fundamental science that we can do at the moon is near and dear to me. We know that large impact craters are ubiquitous on planetary surfaces. One rather small crater on Earth, the Chicxulub crater in Mexico, was largely responsible for wreaking havoc with the Earth’s climate and food chain, triggering a mass extinction of many species on Earth, including the dinosaurs. When you look up at the Moon, the large dark patches are lava flows filling giant impact craters. These craters are 1000 km across and formed in collisions with thousands or millions of times as much energy as the collision that created Chicxulub. To an incoming asteroid or comet, the Earth and Moon appear as a system with a single center of gravity, so whatever hits the Moon has an equal or greater chance of hitting the Earth. So it’s logical that if the Moon experienced these huge collisions, the Earth did too. But where is the evidence on the Earth?

The largest craters on the Moon are very old (4 billion years or more) and they reside in a crust that is 4.5 billion years old. In contrast, the Earth recycles its surface all the time, through erosion, burial, mountain building and subduction. Very few rocks on the Earth are older than 3.5 billion years, and the oldest recognized rocks are a bit of outcrop in northwestern Canada at just about 4 billion years. There are certainly not enough rocks to recognize giant old impact craters at 4 billion years on the Earth. And yet, it was at this time that life was just getting started on Earth. If one medium-sized crater killed more than half the flourishing species in the Cretaceous, what would a hundred giant impacts do to primitive life on Earth?

Some of the outstanding questions about the effects on Earth have to do with how many impacts, how big, and how closely spaced in time. We can’t figure that out on the Earth, because we don’t have the rocks that recorded that information. But the Moon preserves all the evidence if we can just get there and look for it. Moon rocks tell us the timing of large impact events, when and how many, and can even tell us what made the impact, what kind of meteorite. And just like pieces of the Moon get knocked off onto the Earth, large impacts should knock pieces of the Earth onto the Moon, and we might be able to find some very ancient Earth rocks on the Moon (though they will be exceedingly hard to find).

Other way cool science at the Moon has to do with the Moon’s unique atmosphere, which is a combination of outgassing from the planet, solar wind interactions with the surface, and levitating dust; the environment at the lunar poles, where permanently-lit peaks might be good places for solar panels and permanently dark craters might act as cold traps that store volatiles like water; and deploying a network of monitoring stations that can measure moonquakes, the magnetic field, and heat flow from the Moon. It’s also neat to think about the opportunities for new robotic capabilities – with a round-trip communications time of less than 5 seconds, we’ll have a chance to explore as scientists on the Earth interacting with robots on the surface.

Friday, October 20, 2006

Stalking the elusive meteorite

So you’ve all heard, at one point or another, news reports of big fireballs streaking through the sky or of rocks falling from space and punching holes in cars or causing injuries or damage. But those news reports are like twice a year, and halfway across the world from you, and you want to find a meteorite now.

I swear again, I do not plant these questions, but I just put up a new web page a couple of weeks ago, on New Mexico Meteorites, because we get a lot of questions about how to go meteorite hunting. Basically, it takes a lot of patience and time, and you need to be super-careful about whose land you’re on. Other than that, anyone can hunt meteorites. They’re basically irregularly shaped rocks with a black fusion crust and are heavy and magnetic. Unfortunately, that description also fits an awful lot of terrestrial rocks, so check out my other web page on How to Identify a Meteorite, including some easy tests you can do at home. And no, ANSMET team members don’t need to be familiar with meteorites to find black rocks on the ice, but the ANSMET program is funded for scientific purposes by NASA and NSF, so meteorite scientists get first crack at being team members, and as you might guess, there’s no shortage of volunteers from our community, though the project has also taken teachers, writers, photographers and astronauts.

What do you do with a meteorite when you find it? There’s (usually) nothing sketchy about private meteorite hunters. There are lots of people willing to pay for meteorites and if you take the time and money to find one legitimately, you can sell it on the open market. Meteorite hunters and scientific institutions have historically formed a partnership that benefits both of them – scientific institutions will classify and certify the meteorite’s authenticity in return for 20g or 20% of the mass of the meteorite, whichever is smaller. This allows hunters to sell authentic meteorites and scientists to retain pieces for study. In recent years, however, there’s growing concern about private meteorite hunting and selling both from a scientific point of view (frequently, the piece in scientific hands is unrepresentative and we don’t have the money to buy more pieces to really understand the rock) and from an ethical point of view (many meteorites are smuggled out of developing countries in Africa and the Arabian Peninsula by bribing local militias).

I’ll be going down to Texas in a couple of weeks (with explicit, written permission from the landowner) to field test some new equipment we here at the IOM got for meteorite recovery efforts if someone calls us and says they saw a fall, which people often do because the southwestern skies are big and clear. Metal detectors are good at finding meteorites among terrestrial rocks, but can be a pain because they also pick up a lot of spent ammo, aluminum foil and cans, and smelter slag. We’re also bringing a quick chemical test for nickel, with which we’ve had mixed results in lab testing, and a magnetic susceptibility meter, which measures the percentage of magnetic metal in the rock and seems to do a good job of distinguishing meteorites from slag.

Wednesday, October 18, 2006

Meteorites on Mars

Speaking of cold, dry places to find meteorites, there are probably few better environments than the surface of Mars! There may not be concentration mechanisms on Mars like glaciers, but it's probably no surprise that each rover has identified a couple of meteorites, and probably missed others along the way...

Heatshield Rock, now an official iron meteorite named Meridiani Planum

Barberton, one of many rocks left as a lag deposits among the sand dunes of Meridiani Planum, and possibly a stony meteorite

Zhong Shan and Allan Hills, probably iron meteorites on Low Ridge in Gusev Crater

Meteorites: the low-cost, all-natural sample return missions

In just about six weeks, I'll be joining my second season with the Antarctic Search for Meteorites (ANSMET). I'm so excited! This year, I'll be on the reconnaissance team, scouting new icefields in the Transantarctic Mountains to see if any of them have a concentration of meteorites. It means I'll get to see a lot more scenery than the flat ice field where I spent last season! I'll be helping to maintain a web log of our activities, including sending some live data back from the field.

Why do we go to Antarctica to get meteorites? Meteorites fall randomly over the whole Earth throughout time. But, if a meteorite falls in the ocean, or fell 10,000 years ago, it's unlikely anyone's ever going to find it now. Once a meteorite lands, the Earth's forces of water and biology start breaking it down. There are some places on the Earth that are good for finding meteorites when there is a mechanism for concentrating many years' worth of falls in one spot and storing them under very dry conditions. The hot deserts are good for this, where meteorites land among the sand dunes and then when the wind shifts and starts blowing sand away, the meteorites are exhumed. Antarctica is also a good place because meteorites that fall on the glaciers get entrained in the ice (which is actually a pretty dry environment because the ice is so cold it never melts) and carried along the conveyor belt of the glacier. When the glacier runs up against a mountain, the winds convert the ice directly into the vapor phase (like leaving ice cubes too long in your freezer) and the meteorites are left behind. The ANSMET program has recovered more than 25,000 meteorites, or 85% of the world’s meteorite collection.

Why do we study meteorites? The basis of geology is that rocks hold information about the formation and evolution of their parent planet. On the Earth, we can hike around, study rocks in the field, and bring them to the lab for detailed analysis. But we've only collected rocks from only one other planetary field site, the Moon. So meteorites are especially scientifically valuable because they are the only rocks we have from Mars and the asteroids. Even lunar meteorites come from places on the Moon where human have never been and never sampled, and have given us a whole new view of lunar rocks. Remote-sensing techniques, like the spectrometers on our rover friends, are good at what they do but are still a far cry from being able to pick up a rock, crack it open, and measure its isotopic composition to, say, 1% accuracy.

Here's lots more about the scientific importance of meteorites, along with details on how they are collected and curated.

What's an ANSMET season like? You can check out last year's team blog or Linda's PSRD article written after the 2002 season. And, of course, you should tune in to my ANSMET blog to find out this year!

Tuesday, October 17, 2006

Rare meteorites and radar

Here’s another question from the blog comment box: "Riddle me this Science Girl....I just read this story on CNN. What is so new about ground penetrating radar. It has been around for a long time hasn't it? What kind of crystals are embedded in the iron and why are they important? What is with the white gloves? The thing has been in the ground on earth for 10,000 years, isn't that just a little dramatic?"

Pallasites are very rare meteorites. They are basically big crystals of olivine (in gemstone form, olivine is known as peridot) embedded in iron-nickel metal. Besides being incredibly beautiful, they’re scientifically interesting, but it takes a step back to explain why, so bear with me. Like the Earth, many planets heated up when they formed and the materials separated out roughly by density. We see that today on Earth as the crust, mantle, and core. Mars has a similar structure, and so does the asteroid Vesta, and probably so did many other asteroids that have since been blown into pieces by collisions. Pieces that fall to earth of these exploded tiny planets are recognizable as pieces of otherworldly crusts (achondrites) and cores (iron meteorites). We don’t have any meteorites that are definitely mantle material, but the Earth’s mantle is made largely of olivine, and remote sensing of Vesta and the Moon show olivine-rich material in deep craters, so by analogy, we think that asteroid mantles are made of olivine too. Where would olivine mix with metal? At the core-mantle boundary. So pallasites are samples from the core-mantle boundary of asteroids, a relatively narrow zone and so therefore relatively rare.

This specific meteorite, the Brenham pallasite, is one that has gotten amateurs excited for years. Smaller pieces of this meteorite have been found in farmers’ fields all throughout the midwest. Traditionally, meteorites are found by stumbling across them by accident or by systematically sweeping an area by eye or with metal detectors. In the case of Brenham, people suspected there could be more pieces lurking below the surface, and last year, meteorite hunters found the biggest piece of Brenham using a metal detector. The piece described in today's news story was found by combining two pursuits: looking for more pieces of Brenham and validating a hand-carried ground-penetrating radar instrument (that’s the “new” part of the radar) to find local buried resources, like meteorites and water (read more about that in the more explanatory AP story). OK, maybe white gloves are overkill considering all the other organic stuff that’s been crawling over the meteorite, but the recovery party (in part from the curation staff at the Johnson Space Center) was following standard protocol for recovering meteorites, which includes trying not to transfer any human skin oils to the meteorite. While it may have been on Earth a long time, it probably hasn’t been touched by humans ever.

Honestly, I did not plant this question, but it allows me a very graceful segueway into my next planetary adventure: the Antarctic Search for Meteorites. More on that in my next installment!

Friday, October 13, 2006

Conjunction junction and sol 1000!

Today's the last planning day for both rovers before solar conjunction. We're all excited because we're uploading 15 days of plans to each rover to conduct all on their own, then we'll get to drink from the firehose of data return in the last week of October!

The Mossbauer team is excited that we'll be using this chance to collect some fantastic Mossbauer integrations. The Mossbauer spectrometer works by exciting the sample with gamma rays and measuring the emmision and absorption response of the sample. The gamma ray energy on the rovers' Mossbauer spectrometer is tuned to iron, so that the response is a fingerprint of the iron-bearing minerals in the sample we're looking at. This is good because so much of Mars is iron-rich, so the Mossbauer mineralogy has been very useful. But, the Mossbauer source natually decays, and at more than 10 times its expected lifetime, the MB source is fairly weak. This means that to get a good signal-to-noise ratio, we need to leave the MB on a target for something like 48 hours to even get the major mineralogy. To tease out the fine details, it needs more time, and we're almost never able to give it that time before moving on - until now. Both rovers have more than 10 days of Mossbauer spectrometry planned over conjunction. Spirit is looking at her magnet, which has collected magnetic dust along its traverse, to look at what iron-bearing minerals make up the Martian dust from the atmosphere and the ground that gets kicked up by wind. Opportunity is looking at a patch of rock at Victoria crater and I'm super-excited to see what minerals it can find in the rock here!

While we're letting the rovers do their own thing during conjunction, their timers will roll over sol 1000! Since nobody expected them to live this long, much of their software was built to only accept 3-digit sols (up to 999). It's like Y2K for the rover - quick, buy some bottled water and duct tape! The ground and flight software engineers did a fabulous job of either fixing or working around this issue and testing it thoroughly, so we don't expect any problems. Still, I feel like when we next see our little friends, they'll have passed this major milestone.

Mission costs

OK, so there's been some contributed discussion to this blog recently about how wimpy the Mars exploration plans seem to be, and how getting a big rig over there to do it right is really what we need. I don't intend this blog to turn into a political forum, but seeing as it's *my* blog, here's my take on it:

Space exploration is difficult. Space exploration is risky. Space exploration is expensive. Every time a mission fails (because it is difficult), the public demands that the next mission not fail (become less risky) and therefore the price goes up (becomes more expensive). Remember that 90's NASA mantra, "Faster, better, cheaper?" The inside joke was that you could only choose two out of the three.

During the era of Apollo, Viking, and Voyager, space exploration was driven by political pressure, not by science. Each Viking lander cost $1 billion in the early 1970's. That's something like $5 billion in today's money. The Apollo program is estimated at about $100 billion in today's money. Even the Russian Luna rovers are estimated to have cost $1-2 billion each back then. Of course, we have developed more and better technology, bringing the cost of missions down, so using today's technology, a Viking mission might cost $1.5-2 billion. Current Mars Sample Return estimates run from $2 to 4 billion. The reality is that putting a huge drill rig on Mars is not able to happen in the curent climate, where space missions are seen as being driven by science, and society just doesn't think it needs that much science.

I'll accept criticism that NASA, like all big government agencies, spends a lot of its money on bureacracy and could really use more imagination. But even if you were able to somehow cut the costs in half, billion-dollar Mars missions driven by science, however supercool and fantastic science it is, are going to be nearly impossible to fund until society sees them as valuable to them. Let's make a cynical comparison here: the movie Titanic grossed 1.8 billion dollars. Yes, the world's people spent $1.8 BILLION to go see one darn movie. That's three Mars missions right there, for one single movie.

OK, end rant. No more politics. Back to science!!!

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!

Friday, October 06, 2006

Mars: The hip new place to see and be seen

I nearly fell off my chair when my friend on the HiRISE team told me he'd seen us at Victoria Crater. You have to go check out the amazing, new, color images of Victoria as taken by the MRO camera at the HiRISE web page. I snipped out a zoom of the image here, where you can see the little trapezoid that is the rover deck and solar panels, the shadow of the camera mast falling to the right of the rover, and - oh my gosh - Opportunity's *tracks* to her position now on the Cape Verde promontory. Below that, you can also see her tracks out of the lower valley, called Duck Bay. How cool is this?!?!

Here's a link to the MRO Press Release that tells you more about the image.

So this is approximately where Opportunity is now, and will be for the next couple of weeks. Right now, Mars is opposite the Earth in their orbits - For every year that it takes Earth to go around the sun, it takes Mars about two. So sometimes, like last spring and in 2004, Mars and Earth are near the same points in their orbits and close together on the same side of the sun. That's when you can see Mars brightly shining in the night sky (and when you get those email hoaxes that Mars looks the same size as the Moon). In the off years, Mars is on the other side of its orbit from us, and the sun is in between our line of sight, called "solar conjunction" because Mars and the Sun appear to be close in the sky. When this happens, we can't communicate with spacecraft there and everyone takes a two-week break. Last time, the rovers took two weeks off too, but this year, we're radiating 15-day plans to them to continue to do science on their own!