Ever since the FY11 NASA budget came out, I’ve been anxious to see the success of the Falcon 9, SpaceX’s heavy-lift vehicle, and the Dragon capsule. A good Falcon launch and successful Dragon flight demo would be like jumping NASA’s Constellation program straight to an Ares I/Orion system prototype. This is the rocket and capsule that the new budget banks on for ISS resupply and astronaut transport. Of course, SpaceX had already won the ISS resupply contract before the new NASA budget came out, so this really isn’t that big a change from the status-quo solution to the space access gap – except that a successful man-rated Dragon would close that gap entirely!
For the bajillionth time, Mike Griffin’s Constellation Program was on track to do what we did 40 years ago, with what we used 30 years ago, 20 years from now. I know the program says “by 2020,” but it ain’t gonna happen, even with billions of extra dollars.
The new budget focuses NASA on in-space vehicles. Vehicles for carrying people throughout the Solar System. Vehicles for building colonies in space. Vehicles for taking people to planets. Vehicles for exploring planets. The kinds of vehicles that cannot be built on Earth and launched, whole, on a Saturn or Ares rocket. The kinds of vehicles that nobody but NASA would try to build. The kinds of vehicles that would move the human spaceflight program forward!
But, in exchange, NASA is not going to develop boosters. The space agency is going to send its astronauts – still NASA astronauts, dammit! – up to LEO on board vehicles bought from commercial providers. The outcry against this concept is based primarily on the objection that the commercial space access providers are “unproven.”
Well, phenomenal success of the Delta and Atlas lines aside, this is the proving ground. There’s a lot riding on the Falcon 9 flight test; the space community consensus could go dramatically one way or the other depending on the outcome. If SpaceX makes it, we can almost consider NASA fast-forwarded to what Constellation would have done in 2015, or later. (And we’ll be much closer to buying tickets to space!) They just have to buy their launchers from SpaceX, instead of….contracting to ATK to build them.
Good luck to the SpaceX launch crews! Hope the launch is spectacular!
We’ve discussed President Obama’s plans for NASA in my research group. Things look good for us: as a team working on spacecraft technology research, looking for things that will make construction, maneuvering, and other activities in space easier, cheaper, and better, we are very happy to see the technology research arm of NASA finally getting the funding it deserves. (It’s amazingly ironic that “space age” technology means thirty-year-old tech.) However, one grad student in my group questioned the value of targeting asteroids, specifically, for exploration. Is it worth it to send people to asteroids? Do we gain anything by doing so?
I think we do, and I’m going to explain why here. But first, I want to make clear two things I am not going to do. I am not going to make a scientific case for going to asteroids. The reason why I’m not going to use science to justify asteroid missions is that we can gain scientific knowledge wherever we go. We can learn new things anywhere. I’m not going to try to prioritize that knowledge, because in the end, it’s all valuable and it’s likely that there will be breakthrough theories germinated from any field of endeavor. In addition, I am not going to make a case against returning to the Moon or going directly to the Martian surface. I am not going to list reasons opposing either of those destinations simply because I don’t think there are any. Rather, I am going to focus on the reasons why I think asteroids are exciting destinations.
Reason one: Operations on and around asteroids are extremely challenging.
On the one hand, anything in space is challenging. But asteroids may be especially tricky, mostly because we don’t yet understand what being around an asteroid would be like. We have only a few close-up pictures of asteroid surfaces, and have only touched the surface of asteroids with two robot spacecraft that I can think of. As far as we can tell, their surfaces are covered with fine regolith, perhaps like the Moon, but their odd shapes give them very strange (micro)gravity fields. Imagine you’re standing on the “side” of a tiny, potato-shaped world like Ida. Which way is down? Harder question than you might think!
243 Ida and Dactyl
NASA can simulate operations on planets and moons by visiting “analog” sites on Earth, trying out procedures in mock space suits and pretend capsules. NASA also has a wealth of free-fall experience from its operations in low Earth orbit with the Space Shuttle and Space Station. But no space agency has any experience with or ways to simulate environments like asteroids. So, not only are asteroids tricky places to be, but the only way to learn about being around asteroids is to go to an asteroid. We’ve never done or thought about this stuff before, at least not in detail. I think that’s exciting!
In particular, I think the challenge of operations around asteroids demands that we send people there. There has been a lot of talk about how the new NASA plans will leave our astronauts without jobs and focus entirely on robotic missions. Whether you think that is a good thing or not, I think it is untrue. While robotic precursor explorers will give us some inkling about what to expect, figuring out how to actually do things on asteroids (science, construction, etc) may be better achieved through an in-situ human learning process. The closest analog we have to asteroid operations is work around the outside of ISS, which we do not yet trust to robots and have tremendous experience with. Astronauts around asteroids could rapidly tell NASA Mission Operations analysts what the major differences are between an ISS spacewalk and asteroid spacewalk. At the same time, a human’s ability to learn on-site, manipulate four limbs in a coordinated manner, and perceive situations clearly and directly would be desirable qualities.
Why do we care about learning how to operate crewed missions around asteroids? Well, Reason Two is that these asteroid operations skills are transferable.
Buzz Aldrin likes to talk about Phobos. Well, if we want to go to Mars, then the first question we must answer is exactly what sort of mission profile we want to use. Options include a Moon-landing-like sortie mission, in which we put boots on the planet, bounce around picking up rocks for a couple weeks, plant a flag, and then take off for home. We could also send a mission that lasts a year or two and involves building a temporary (or permanent) base, establishing laboratories, and zipping around in rovers; this probably involves multiple launches to and from the Red Planet. Or we could go for the interesting option of picking 50 or so people and sending them to Mars, in one launch, with everything they need to be self-sufficient. The point of all this is that, depending on the mission, it might be valuable to use Phobos as a way station. And if we want to be around Phobos, we have to learn how to be around Phobos. More than that, we have to learn how to be around Phobos and be very, very far from and out of reach from Earth.
Moreover, microgravity operations around small bodies are exactly the kinds of operations that would be relevant in the asteroid belt. Or around the Jupiter Trojans. Or in Jupiter’s moon system. Or Saturn’s moon system. Or near comets. Or by near-Earth asteroids. You get the picture: small-body operations will be important for the manned exploration of the Solar System beyond the Moon and Mars, and the more capabilities we develop, the easier it will be to get to and function in exotic places.
Next, reason three: not only is there science to be done, but around asteroids, we could learn techniques that may be necessary for Earth defense.
Yeah, I’m talking about defending the planet from rogue asteroids. We certainly won’t be doing this by launching a team of misfit miners and Bruce Willis. Now, the asteroid deflection techniques we develop may or may not involve manned missions, but when we’re talking about the survival of a city – or the entire human race as we know it – why remove any tool from our kit?
The fourth reason is one that ought to appeal to space technologists out there: asteroids could provide resources for construction which are much easier to get into orbit than the resources on Earth.
Asteroids are made of useful things. Nickel-iron asteroids are composed of metals, both common and rare. Carbonaceous asteroids contain other materials. Some even have organic compounds. There is even recent evidence that many asteroids have water! These potential resources may be easy to get to, if the asteroids are rubble-piles, or the useful materials are in the asteroid regolith, or if the asteroid is entirely made of metals that can be melted or dissolved for processing.
Budding space industrialists may be disappointed, but mining asteroids for rare metals to sell on Earth isn’t likely to be economically viable. (It’s too hard to safely get those metals from the asteroids down to Earth’s surface – for instance, we would have to spend more money to launch a Space Shuttle than we would get for the mass of materials that Shuttle could bring down from orbit – a launch costs roughly $450 million, and at current prices, the Shuttle could bring down $15 million in pure silver if filled to the brim. We’d have to find asteroids made of pure gold and platinum and cram the Shuttle to make that come out positive.) However, what could be viable is mining and processing the resources on asteroids into spacecraft bodies, components, consumables, and fuels, which could be jettisoned from their parent asteroids with very little effort. This is simply because asteroids have very small escape velocities compared to planets and moons. If we could get ISRU going, it could be the great moneysaver of the space industry!
ISRU, or in-situ resource utilization, is already a hot topic of research; applications include processing lunar regolith into bricks or reacting chemicals with Martian soil to produce rocket fuels. This would be the next level of complexity: imagine landing a facility on an asteroid that grapples to the rock, bores its way down, processes the metals in the asteroid, and extrudes spacecraft pieces that are ready to assemble. Or perhaps a spacecraft that can land on an asteroid and scoop up material to refill its fuel and consumables. These abilities would let humans build whole new classes of spacecraft, capable of going further than any before. And, given the complexity of building the International Space Station, many of these activities will probably require the involvement of astronauts.
The last reason I can think of – at least, right now – why asteroids make very cool targets is that the asteroids themselves could be used as spacecraft.
The science-fiction way to do this is to find an asteroid and hollow it out with tunnels, crew compartments, fuel tanks, or big, cylindrical chambers. The excess rock and metal from the digging can be fed to mass drivers (or combined with antimatter) to propel the asteroid.
As big a fan as I would be of asteroid colonies or arkships to the outer Solar System and beyond, that’s a pretty farfetched idea at this point. However, an interesting possibility if we want to get to far-flung destinations is to locate an asteroid in an orbit that starts somewhere easy to get to and goes somewhere we want to go, and then hitch a ride. There’s an interesting class of resonant orbits called “cyclers,” which have the property that they rendezvous with two bodies of interest at least once per synodic period. For example, the so-called Aldrin cycler is an orbit trajectory that matches up with the Earth and Mars, with a travel time of 146 days between planets. All we’d have to do is get there and grab on!
We’re not likely to find an asteroid that is naturally on such an orbit, but we may locate asteroids that are on other potentially useful orbits. If we learn enough about asteroid deflection from our planetary defense studies, we might even be able to nudge asteroids onto such orbits, on purpose!
The Moon is a cool place to go. Mars is a cool place to go. Jupiter is a cool place to go. But, you know what? Asteroids are cool places to go, too. We will learn and benefit from any exploration destination. Small bodies, which come in all sorts of shapes, sizes, and compositions, may be very, very different from planets and moons. If we can learn how to use them as platforms for exploration, then perhaps we can jump off them to explore all the far reaches of the Solar System.
The Space Shuttle mission which just undocked from the International Space Station, STS-131, has beamed down from orbit some great photos of astronauts in space. This is a wonderful chance for us stuck planetside to remind ourselves that we have people living and working in spaceships!
The Discovery crew in the Cupola
And, of course, this mission is historic for having the largest number of women simultaneously in space – four out of the thirteen total crew. Considering small-number statistics, that is pretty close to a fifty-fifty split! Here is the orbiting Bay Stater, Stephanie Wilson:
MS Wilson in the Kibo laboratory
And here’s JAXA’s Naoko Yamazaki in the Destiny laboratory at a robotics console made of lots of ThinkPads taped to the ISS wall,
MS Yamazaki in Destiny
although I think this is my favorite picture of Yamazaki!
While President Obama’s speech this afternoon wasn’t a slam-bang Kennedyesque dream vision, I thought he expressed some good ideas. Of course, there aren’t too many substantial differences between the plan we heard and the plan Charlie Bolden presented in February; the President’s remarks today sounded much more defensive than visionary. Given the amount of criticism his NASA ideas have received, I don’t really blame him…but still.
The most frustrating thing to me about the new NASA plan is how distorted it has become in the media. The first thing Obama said this afternoon was that he is increasing NASA’s budget by $6,000,000,000 – at a time when he has frozen discretionary spending and we are looking for ways to deal with crisis after crisis. There were even headlines two days ago to that effect. Ohmigosh, the budget is going up! Well, yeah. It went up in February. It’s a wonder that the story in the media since then has been uniformly about NASA budget cuts; that attitude has permeated commentary even from sources inside NASA. It’s amazing how an idea like that can spread, even in the face of direct evidence of exactly the opposite.
Most of President Obama’s remarks today were familiar to me. Billions of dollars for robotic precursor missions, game-changing technology research, technology demonstration missions, and new human spaceflight capabilities. Buying launches from American companies rather than having NASA contract out for launchers to call its own, to close the LEO access gap. Extending the Space Station. All this we’ve seen before, and I still think all this sounds good.
We heard about two new development programs this afternoon: an ISS crew-escape vehicle based on the Orion capsule, which will evolve into our deep-space crew vehicle designs, and an accelerated heavy-lift program with the goal of having ready-to-build designs by 2015.
The Orion-derived crew lifeboat I think is stupid. To me, this looks like either pandering to the people at Marshall Space Flight Center who were annoyed that they didn’t have a capsule to build, pandering to the people who think tat a Dragon capsule wouldn’t meet NASA safety requirements, or pandering to the pining-for-the-Cold-War neocons who have been crying about how our ISS astronauts will be “held hostage” without US access to space. Having an ISS lifeboat may sound like a great idea, but the station already has a few reliable Soyuz vehicles for exactly that purpose. An Orion lifeboat is a waste of money and effort. The one good thing about this program is that it is supposed to feed into our designs for true space vehicles – but I would have preferred it if the President had just told the Orion teams to concentrate on that purpose.
The accelerated heavy-lift program is more exciting. I’d love to see NASA developing the capacity to fling wonderful new hardware to high Earth orbit and beyond, and I understand that it is valuable to keep the engineering expertise to develop such a vehicle within the NASA organization. I’m very happy to see a date of 2015 attached to the designs for that system – and remember that Ares I was projected to be ready no earlier than 2018, and Ares V around 2030 – so the new heavy lift program is a much more ambitious one than either of these!
In addition to these new programs, President Obama finally announced a series of targets and dates. Criticisms of the new NASA vision have come from all across the board and contained all sorts of specific elements – but the one shared element, heard from ’round the space community, were: where is NASA going? and when is it supposed to get there?
Well, today we heard the following:
Ready-to-build heavy lift designs complete by 2015.
Human crews fly beyond the Earth-Moon systembefore 2025.
Human crews land on an asteroid sometime between 2025 and the mid-2030’s.
Human crews orbit Mars by the mid-2030’s.
Human landings on Mars are supposed to follow “shortly thereafter.” I’m thrilled to see these dates; they are nicely within my lifetime and identify specific targets. Perhaps they could have been presented with a bit more polish and panache, but I’m happy to have them!
(Side note: The Augustine Commission found that, with $3 billion/year extra funding, the Constellation Program would miss its 2020 deadline and get us to the Moon around 2030. So….eat it, Mike Griffin.)
Finally, I want to comment that it occurs to me that a lot of people in the space community have been contrasting Obama’s new plan to Kennedy’s speeches in the early ’60s. Obama’s speech today couldn’t have illustrated the differences between the two Presidents’ characters better – Kennedy seemed to run on pure emotional vigor in his space speeches, while Obama was his usual cool, collected, rational self. I like what he’s planning, but it wasn’t exactly couched in stirring rhetoric. However, I don’t think that speaks poorly of Obama’s commitment to space exploration. I think the difference between Obama and Kennedy is simply one of pragmatism. When I look at the goals he laid out, and compare them to Norm Augustine’s comments at the opening of the space summit (made as I began this post!), they make a lot of sense in that light. What Augustine said is that NASA’s goal, in the eyes of his commission, the NASA administrator, and the President, is to land people on Mars – but the trouble is that we just don’t have the technological capability yet to do that. Obama’s vision for NASA starts with developing that capability.
Put another way, imagine Kennedy had Obama’s character. His stated goal, expressed in that famous speech to a joint session of Congress shortly after Alan Shepard’s first flight, would not have been to land a man on the Moon and return him safely to the Earth. It would have been to develop and demonstrate technologies like orbital rendezvous, multi-person spacecraft, computer control of spacecraft, heavy lift, and planetary landing stages. Essentially, it’s as if Kennedy’s goal had been to complete the Gemini program. But the deadline for completing that goal would have been shorter than a decade, and the story wouldn’t end there. The groundwork would be in place for whoever was President at the time of Gemini’s completion to say, “okay, we’ve got that under our belt…now let’s get to the Moon!”
In short, Obama could have said something like, “Let’s land on Mars by 2040!” But instead, he gave us more incremental, shorter-term goals with a much higher chance of success. And he laid the groundwork for a future President to say, “okay, we can keep people alive in space for years and get to Mars orbit…let’s put boots on the ground!”
I recently spent over a week in full research-promotion mode, and I’m finding it tough to switch back into research-doing mode. Coincidentally, I don’t think I’ve actually written a blog about my graduate research yet, though I’ve put descriptions of it on both my personal web site and Cornell group web site. So, I’m going to try and get it all out of my system…
Suppose you ask: Hey, Joe! What’s your research about?
Well, it’s about building Transformers in space out of Legos connected by tractor beams. Seriously. Okay, fine, they’re not “tractor beams,” more like…”tractor fields.” But other than that, not a bad description. Here’s an old-ish video version:
I demonstrate flux pinning
First: Why?!
There are a lot of possible reasons why we ought to be thinking about building large-scale structures in space. Imagine assembling a huge space telescope out of hundreds of mirror segments, giving the telescope an effective light-gathering area of hundreds of meters and letting us peer into the dimmest corners of the Universe – from the most distant objects to extrasolar planets. Or, if we’re interested in space-based solar power (putting solar power collectors in space, where they could gather sunlight 24 hours a day without atmospheric filtering, and then beaming that power down to Earth) we would want to make the biggest collector area we can. Proponents of geoengineering approaches to climate change mitigation have been seriously considering constructing a giant sunshade to reduce solar incidence on the Earth, a short-term solution that could stave off environmental impacts while we work up longer-term fixes. And finally, if we want to maintain a long-term human presence in space – from Mars explorers to microgravity research and manufacturing technicians to paying space tourists – we will need vehicles and stations with enough room to accommodate many people, hold life support and other supplies, and provide equipment to stave off the detrimental effects of microgravity on human physiology.
All of these possible applications – any one of which would have tremendous implications for our lives on Earth – demand that we build a large structure in orbit out of smaller components. The reason for this is simple: launch vehicles can only carry so much mass and volume into orbit. Those limits are on the “stowed” size of spacecraft, so we do have the option to build craft that deploy, or unfold, out of their tightly-packed, mostly cylindrical launch configuration and into some more spindly and useful shape. For example, most Earth-orbiting satellites get their power from large solar panel “wings” that would not fit into a launch vehicle fairing unless rolled up in some clever way. There’s a lot of research these days on inflatable spacecraft, that could expand to many times their stowed size and get structural support from their internal pressure, but even those balloon-like craft cannot get indefinitely bigger than their launch envelope. Deployments and inflatables only make the volume or length of the spacecraft larger – so, for the same mass, you end up with spindlier structures, which might be fine for some applications but not others. So, in order to get the really big spacecraft, we must assemble smaller pieces to make the final system. Think of the International Space Station assembly process. Continue reading Hey, Joe! What’s your research about?→
First, Ryan has posted an excerpt of a speech by Charlie Bolden addressing common misconceptions about the new NASA budget. The speech confirms that (1) the goal of the US space program is to get people to Mars, (2) NASA will be pushing the technological envelope to do that, (3) the human presence in LEO will be going full-throttle all that time, and (4) Constellation was going to fail at all those things. I’m happy.
Second, the Big Picture has a great series of photos from the 2010 Vancouver Paralympics. It’s a fantastic collection of photos, and I wonder why those events aren’t televised. Many of them look even more exciting than some of the analogous Olympic events. Best wishes to those athletes!
This *almost* made me register for Twitter, just to respond. But I am still resisting the “service that nobody knew they wanted!” I hope a pingback goes through…if not, I bet I can rely on a retweet from @aerognome. 😉
Here are my answers:
1) Should Constellation be saved?
No; at least, not without a lot of major changes. CxP is drastically underfunded, horribly over budget, way behind schedule, and myopically limited in technology and innovation. It wasn’t going to get us to the Moon before 2030 and wasn’t even going to get us to ISS before 2018. I’d very much like to have Mike Griffin’s Constellation fetters come off.
2) Should Shuttle be extended to close the gap?
No. Not only is that infeasible (there are no more STS external fuel tanks left, and we cannot make more) and uneconomical (due to high launch and recovery costs), but the Shuttle is thirty years old. It was never designed to fly for this long and should have been replaced in the early 90’s. In what other industry do people go around with 30-year-old vehicles and devices, still saying that they are the cutting edge? In what other industry is the 30-year-old vehicle the cutting edge? This is your own damn fault, Congress. Where’d the X33 go when we had the chance?!
3) Should NASA perform exploration missions while developing new R&D technologies that will get us to Mars?
Yes, and I don’t think this point is at issue. The problem is that the Obama administration chose to release their NASA budget without a corresponding space policy speech – it’s not that exploration missions have been cancelled, it’s that we don’t have any information on exploration targets and goal dates. I suspect that Obama’s rumored speech in April will remedy this. At least Charlie Bolden thinks we’re going to Mars!
It is important for me to say that there is a corresponding question, “should NASA develop new technologies while performing exploration missions?” The answer to this question is also “yes,” and critically, it was “no” under Constellation.
4) Is a heavy-lift vehicle required to leave LEO?
Let me instead answer a more general question: “Are new technologies or vehicles required to leave LEO?”
To that, I say yes. Either that means we need an economical heavy-lift capability, or tech development related to in-orbit deploying and assembling of large structures from small components. A detailed trade study should show which of those options to pick.
5) Why is inspiration important to the future of NASA?
Our nation is increasingly facing challenges that must be approached by scientific or engineering methods, and so it is generally in our national best interest to get students studying STEM fields. One way to keep them interested in science and technology is to make sure that there are really high-profile science and engineering project being done on a national level – the kinds of projects that happen at NASA. Even if those who pursue STEM fields don’t work for NASA itself, they may tackle related problems that have national repercussions, from more efficient solar cells to better medical technologies to indefinitely preservable foods.
And of course, NASA needs a pool of motivated, educated, capable recruits in order to pull off such projects. So NASA itself has a vested interest in inspiring students to remain interested in STEM fields during and after their educations.
My blog had been trucking along with a reliable readership of perhaps a dozen people, when, suddenly, after a slightly stream-of-consciousness post about the physics of space combat, Gizmodo asked to reprint the material from my blog. It was never my intention to get so much attention – but apparently that article turned into the most-commented content on Gizmodo that week! I got lots of questions and comments and emails after that and noticed lots more pingbacks on my blog entries afterward.
I couldn’t help but think, “Wow, if only my research activities would generate this sort of interest! I’m trying to build tractor beams and wrote up my experiences from Vomit Comet flights. How is that not cool enough?!” At least I got to abuse my 15 seconds of Internet fame to plug NASA a bunch!
Well, just a couple weeks ago, Karl Haro von Mogel from the University of Wisconsin, Madison, contacted me to interview me for his radio show, “The Inoculated Mind,” which airs on the student radio station in Madison. This was my first on-air interview, and I had a lot of fun with Karl! You can listen to a podcast of the show on his web site. It sounds from the beginning of his show that Karl and I would get along nicely, and then a little before halfway through he plays the interview. If I sound excited, it’s for good reason!
Many thanks to Karl for having me on his show, and for chatting with me about my research as well as the sci-fi stuff! (Oh, what the heck, my research is practically about science fiction, too!) And great use of Battlestar Galactica music and lead-in with the science of Avatar’s unobtainium!
And, of course, a link to the short story Karl brought up: High Orbit. Enjoy!
Just as a freebie, after the jump I am going to list several common questions and comments I got after Gizmodo picked up my initial blog, and respond to them a little bit. I am falling for exactly the issue that Phil Plait identified in his comment on my post – this could go on ad infinitum! So I’m done with this post now, but if you want even more about space battle physics, click here: Continue reading revenge of space combat physics→
Phil Plait of Bad Astronomy posted a few days ago about caved-in lava tubes on the Moon. This isn’t really new news, but it’s still pretty darned cool news. He posted some images of the cave. However, I found a major, glaring error in the LROC image data.
I fixed it.
Lava cave - fixed!
Seriously, though…those sites are perfect premade Moon base locations. Imagine a team of astronauts putting an inflatable dome over the hole in the roof, belaying down there, putting inflatable endcaps a few tens of meters down the lava tube in each direction, spraying expandable foam sealant into all the crevasses, and using some ISRU atmosphere generators to pump the tube full of oxygen.
I know I am not at my blogging best when I just write, “hey, look at these spectacular images!” But…look at these spectacular images!
An image-of-the-day gadget on my iGoogle home page showed me this picture, which I subsequently spent about a half hour trying to locate at a primary-source web site. It is wicked cool.
Possible Cyclic Bedding in Arabia Terra (HiRISE/MRO)
Click to go to this image’s description page on the University of Arizona HiRISE site. (Be sure to bookmark the 2560×1600 wallpaper version!!!)
I really want to know how these terraced buttes got to be the way they are…it looks like they must have been eroded in stages, with each layer from the top getting peeled back successively, but somehow the individual layers hold together – those are some pretty steep walls. I can see in the southwestern portion of this image that some of the terrace walls are eroding away in chunks; there are a couple good fallen boulders over there. The layers might be some kind of sandstone, because they haven’t eroded away in lots of rocks and boulders, so they don’t seem very friable, but there’s obviously a lot of source material for dunes in this area so the butte walls might be getting ground down into very small grains. I’m not sure what the fluvial history of Arabia Terra is – on Earth, that would be bound to play an important role in creating landforms like this.
I also really love the expression of the more recent aeolian features in this area. Looks like there are prevailing north-south winds on the east side of this image (I’m going to say the wind blows to the north because the north sides of the dunes look more like slip faces to me), but from the east-moving dunes in the terraced valley-like feature at center bottom and the east-west oriented ripples on the larger dune field, the winds are apparently going in rather circuitous routes around these buttes. There are also some confusingly-oriented dunes and ripples in the southwest portion of this image, probably from the wind winding around all the rocky towers. (In my mind, I can hear it whistling.)
Looks like the valley from which the east-going dunes have traveled is an exposed outcrop of one of the terrace layers. This image can resolve objects less than a meter in size, so the various crisscrossing dark lines in the light-toned outcrop might be joints or something.
Anyway, this is not a new image and I haven’t studied or researched this stuff…I just saw it today and wrote a little stream of consciousness of geological ideas. I just think this image looks beautiful and I want to send some rovers/people there. Any planetary science guys want to comment?
Last, and just for grins, here are some goodies I turned up in my search for that image on the UA HiRISE site. Here we have some dramatic contrast between dunes and some lighter, rockier topographically high areas:
Pitted Layers Northeast of Hellas Region
Here’s some great layer exposures around some hills – and if you zoom into the large version of this one, you can find some wild and interesting ripple patterns:
