Archive for the ‘ESA’ category

Rosetta flies by Lutetia

July 11, 2010

You do know about ESA’s Rosetta probe don’t you? This european mission to the comet 67P/Churyumov-Gerasimenko (say that three times fast!) launched in 2004 and has one of the most convoluted mission timelines I’ve seen. Here’s a graphical version, followed by a list of key events. You can also click the image to read the text better.

  • First Earth flyby (March 4, 2005)
  • Mars flyby (February 25, 2007)
  • Second Earth flyby (November 13, 2007 )
  • Flyby of asteroid 2867 Šteins (September 5, 2008)
  • Third Earth flyby (November 13, 2009)
  • Flyby of asteroid 21 Lutetia (July 10, 2010)
  • Deep-space hibernation (May 2011 – January 2014)
  • Comet approach (January-May 2014)
  • Comet mapping / Characterisation (August 2014)
  • Landing on the comet (November 2014)
  • Escorting the comet around the Sun (November 2014 – December 2015)

As you can see, yesterday, Rosetta had a flyby of the asteroid Lutetia, and there are some stunning images coming down. Let’s take a look at the closest approach image:

Lutetia as seen by Rosetta at a distance of 3162 km. (Click for larger version)

Of course, the first thing to notice is that Lutetia has a very irregular shape, as expected for an asteroid. It is about 100km in diameter, and is peppered with craters ranging from big basins that change the whole shape of the asteroid, down to tiny pits. One thing that stands out to me is that the surface appears to have lots of linear features. Similar lines of pits are visible on Phobos, one of the moons of Mars. The grooves on Phobos are more pronounced than the ones on Lutetia, but the similarity is still there. One hypothesis for the Phobos grooves is that they are formed when impacts on Mars, launch streamers of debris into orbit, which then impact Phobos and form a chain of craters. This process wouldn’t work for Lutetia because it isn’t orbiting a convenient source of ejecta.

The grooves could also be cracks, possibly caused by the big impacts that formed the giant craters on Lutetia. Another possibility is that the lines have to do with the way asteroids are held together. I heard a talk at LPSC this year about the role of van Der Walls forces in asteroids. (For those who have forgotten their high school chemistry, van Der Waals forces are what makes small particles cling together even if they have no net charge). The idea is that on asteroids, the particles are much bigger than we usually consider with van Der Waals forces, but gravity is so low that the forces are still important. In other words, the best analogy for rubble pile asteroids might actually be something like dry flour rather than a pile of rocks and boulders! And if you’ve ever packed flour in a measuring cup, you’ve probably noticed that it can “crack” even though it’s barely held together. The same thing might be true of objects like Lutetia and Phobos!

I’m not an asteroid expert at all, so I can only imagine what the true asteroid afficionados are getting out of these pictures. I’ll keep an eye out for results from this flyby at conferences!

As for Rosetta, it’s back out into lonely space for a few years until finally catching up with comet 67P and conducting its primary mission: orbiting and landing on a comet!

Barnstorming Mars

June 2, 2010

You need to check out this video that the ESA just posted:

This was compiled from the small “Visual Monitoring Camera” on Mars Express, and it gives a beautiful view of what Mars looks like from the spacecraft’s highly elliptical orbit. I love the way the orbit clearly speeds up as the spacecraft swoops by the pole. Also, pay close attention at the very end and you can see a dark spot cross the planet: that’s Phobos, one of Mars’ tiny moons!

For a more detailed discussion, check out Emily’s post on this awesome video!

AGU 2009 – Day 1

December 16, 2009

For those not familiar with the conference, the fall meeting of the American Geophysical Union is a terrifyingly, overwhelmingly large conference. Each year, something like 16,000 geoscientists descend on San Francisco to share their work. It is also one of the major planetary science conferences, so a lot of new results are first presented here.

Moscone Center in San Francisco. This building is filled with science at every fall AGU meeting.

This year, the first talks that I checked out on Monday were about radar observations of Mars. By sending radar waves from spacecraft to the surface and then recieving the reflected waves, we can learn a lot about Mars. In particular, since radar penetrates tens to hundreds of meters below the visible surface, it can reveal otherwise hidden structures. This has been especially successful at mapping the structure of the polar caps, because radar penetrates through ice quite well.

Roger Phillips gave a talk summarizing some of the results from the SHARAD radar instrument on MRO. Among other thers, SHARAD has found evidence that the spiral troughs in the north polar ice cap have migrated over time, as predicted many years ago by theoretical models. SHARAD has also found ancient buried canyons in the polar ice, which menas the ice caps have been around for quite a while. There are also some exiting new results implying that the material filling valleys in the Deuteronilus Mensae area is quite transparent to radar waves, and might in fact be something like glacier ice.

Image credits: NASA/ESA/JPL-Caltech/ASI/University of Rome/University of Washington St. Louis

After the radar talks, there were a whole bunch of presentations about aqueous alteration on Mars. One of the main lessons that I took away from those talks was that Mars is still a very confusing place. For example, Hap McSween used data from the Mars rovers and characterized typical soils at both landing sites. He found that the compositions of soils are roughly 70% unaltered material and 30% alteration products. He also showed that the soil compositions are quite similar between the two landing sites, which are on opposite sides of the planet, and that the unaltered portion of the soil is similar to the rocks at both sites.

However, the next talk by Josh Bandfield used orbital data and found that in general rocks on Mars have more of the mineral olivine than the soils. This is a somewhat different result than the rover data, and it might imply that rocks on Mars actually have more magnesium and iron than previously thought.

Other talks related to Mars alteration focused on “clay” and sulfate minerals detected on Mars. One that I found particularly interesting was by Paul Niles, who pointed out that Mars is an “obliquity-driven” planet. In other words, its tilt varies widely, and the Mars we see now is not typical. Niles suggested that during more typical periods, ice might have formed large layers at Mawrth Vallis, a location known for its strong hydrated mineral features. Melting at the base of that ice could have leached the rocks, explaining the presence of specific Al-bearing clay minerals.

Map of water-bearing minerals at Mawrth Vallis. Image credit: ESA/OMEGA team

Another interesting talk was by Itav Halevy, who took a look at how the presence of SO2 gas influences the formation of carbonate minerals. It turns out, even a tiny amount of SO2 gas (which is often released by volcanoes) can prefent the formation of CaCO3. If there is iron around, FeCO3 (the mineral siderite) forms instead. The implication is that sulfur minerals should form in different locations than clay minerals and siderite.

Continuing with the sulfur theme, Albert Yen talked about some results from the Spirit rover. He said that basically, if the rover had to get stuck, it picked a really fascinating place to do it! Based on the compositions measured, it turns out that there is too much sulfur in the soil to balance it out by assuming it is combined with other elements like Fe and Mg. That means there might be pure elemental sulfur mixed in with the soil, which would be consistent with hydrothermal activity!

My officemate and occasional contributor here at the Martian Chronicles, Briony Horgan, also gave a nice talk summarizing some of her recent work. For a long time there has been a question about the so-called “surface type 2” on mars. This surface type has higher than usual Si, but that could be due to a different type of lava, or alteration of the more common basalt seen elsewhere on Mars. Briony presented new evidence, based on the overall shape of the spectra of surface type 2 regions, that these areas might be due to a silica glass coating! This sort of coating could form when thin films of water from thawing ground ice altered the surface of sand grains, and would imply relatively recent alteration processes on mars.

Finally, the day ended with the Whipple prize lecture, which was unfortunately full of some misleading information about the history and status of Mars science. But that’s the topic for a future post.

A single Mars program for the Earth?

December 4, 2008

One interesting tidbit that came out of the NASA presser on the MSL delay are comments made by NASA Assoc. Admin. for the Science Mission Directorate, Ed Weiler. Apparently, NASA and ESA have gotten clearance to start laying the groundwork for a joint Mars program. As Ed Weiler said:

So David [Southwood – ESA Director of Science] and I sort of talked about the possibility of maybe we oughta think about NASA and ESA getting together and come up with one Mars architecture, one Mars program for the Earth… In the future, NASA and ESA are going to work together to come up with a European/US Mars architecture. That is, missions won’t be NASA missions, they won’t be ESA missions, they will be joint missions. We need to work together. We’ll never, ever do a sample return mission unless we work together.

This is a really interesting proposal. Making space exploration a more international endeavor is a big challenge, but has been cited by many (e.g. the  Planetary Society) as the only way to accomplish the broad goals of robotic and human space exploration.

This idea also is coming up at a time when the future of the Mars program is totally up in the air. The “2016” rover mission and the ever lingering sample return mission had been moved to the edge of the map even before the MSL delay. International collaboration will probably help both to establish a more concrete timeline and spread out the cost for these missions. The 2016 surface mission was specifically discussed as being much more likely in the international context, presumably as some combination of ESA’s ExoMars and the 2016 US mission. As Ed so eloquently put it:

It’s nice to put our logos on our missions… but we could probably do a heckuva lot better mission if we did it together than if we continue to compete with each other.

While I think this will overall be a huge boon to Mars exploration, there are certainly hurdles that will have to be overcome. ESA and NASA have very different management styles, as do the science and engineering teams under each. ESA also has a very different relationship with it’s supporting governments than NASA does in the US. It will certainly be interesting and instructive to watch this process take place from within the science community.