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Methane on Mars

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NASA has announced yesterday the discovery of methane in the Martian atmosphere, and that has become huge news quite rapidly; I've even seen it mentioned on TV earlier today.

Why is that an important discovery? Well, methane is a very fragile substance; not only UV rays destroy it quickly (by breaking the atomic bonds), but so do exposure to oxygen or hydrogen peroxide. Mars lacks an ozone layer, so UV rays are very abundant there, and oxygen and hydrogen peroxide are not that hard to find either. Taking all that into account, the fact that there is any methane at all in the atmosphere means that it is being created and released by some process.

On Earth, most processes that release methane are biological. Bacteria release large amounts of it while processing organic matter, and so does cattle (technically, the bacteria in their guts). We know there is no cattle in Mars, but we can't rule out underground bacteria.

There are geological processes that can release methane as well; however, it is (was?) thought that Mars is pretty much dead, geologically speaking. So, this discovery means that either there are some previously unknown geological processes going own in the red planet, or there are biological processes. Both possibilities are very exciting, but it will take a while before this can be settled.

Mars keeps surprising us, and I don't think it will stop any time soon!

Mars as a real place

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One of the great things about the Mars exploration program, brought about by the huge amount of high-quality images being sent by all the hardware we have there, is the sense of Mars as a real place. You know, not just as a dot on the sky, or this distant abstract "thing", but an actual place, as real as any place we have here on Earth, where things actually *happen*.

The first ground-level images we got from there, from the Viking crafts, were a start — but they were basically static. The idea was that of some unchanging expanse of rocks and dust, sort of like to Moon but with a bright sky. But the truth is very, very different.

In recent years/months, thanks to several missions (the rovers Spirit and Opportunity, the Mars Reconnaissance Orbiter, Mars Express, the Phoenix lander and others) we got (click on images for larger versions, follow links for more info):

I think the impact of those images, especially the animations, comes from our sense of celestial objects as places where changes take eons; they show us that this is not the case, that our neighbours can be dynamic, changing places. They give me a sense of the enormity of the universe, more than even the Hubble Deep Field did, because they make it seem more real. If all this is happening in our nearest neighbour... what else is happening everywhere else? What other wonders are we missing out there?

The universe is a great place, even if it's trying to kill us. I hope it won't be too long before more of us get to experience more of it.

More exoplanet images?

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2008-11-22-bpictoris.jpgNow, this is not 100% confirmed, but it does look like we've got another image of an extrasolar planet: this one (if real) is orbiting the star β Pictoris, a very young star 70 light-years away from us.

The potential discovery comes from a new analysis of images taken in 2003 with ESO's Very Large Telescope. The images were processed to subtract from them the light coming directly from the star, allowing scientists to see objects that are around it; this showed a very distinct point of light very close to the star and in the same plane as the dust ring that surrounds it, but we can't still rule out the possibility that this is a background or foreground object instead of something actually in the neighbourhood of the star.

If this is a real planet, it is closer to its star than the other ones imaged previously, being approximately as far from it as Saturn is from the Sun; it would be a very large planet, though, about eight times as massive as Jupiter.

New observations might prove this object to be a planet (by showing its movement around the star, presumably), so we will definitely hear more about β Pictoris in the future. More details at the ESO press release.

Extrasolar planets imaged directly

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2008-11-14-fomalhaut.jpgThis has been the talk of the Internet today, so I might well write about it as well... for the first time, scientists were able to capture images (in visible light, no less) of not one, but four extrasolar planets orbiting around two separate "normal" stars (we had already seen images of a planet orbiting a brown dwarf star).

First, we have star HR8799, a young star that is a bit larger than our Sun (1.5 times as massive and 5 times as bright) and that lies 130 light years away in the constellation Pegasus. Images taken with the Keck and Gemini North telescopes in Hawaii show three large planets orbiting this star; one is about seven times and other two are 10 times as massive as Jupiter. They orbit the start at distances ranging from 24 to 67 AU (the planetary limits of our own solar system are around 30 AU).

Apart from the historical value of directly imaging these planets, this event is significant for other reasons: this star is very similar to our own, and these large planets are orbiting it at a large distance, leaving space closer to the star for small rocky worlds; in other words, this might be a solar system similar to our own, which is something of a rarity among the hundreds of other solar systems we've already found.

Secondly, we have Fomalhaut, a larger star (2.3 times as massive and 16 times as bright as the Sun) 25 light years away in the constellation Pisces Austrinus, the southern fish. It's been known for a while that this star is surrounded by a large dust disk; in fact, the very sharp inner edge of this disk was a clue that there was a planet there, cleaning out debris just inside the disk. And, indeed, Hubble images do show a bright planet located there, in a very wide orbit around the star. The planet seems to be about twice as massive as Jupiter, and its brightness may indicate it is surrounded by a very large ring system.

The planet orbits the star once every 872 years at a distance that is almost four times the distance from Neptune to our Sun, but since Fomalhaut is brighter than our Sun its appearance would be similar to how the Sun appears when seen from Neptune. Just as is the case with HR 7899, Fomalhaut is a very young star and its solar system is still being formed, which helps in the detection of the planets: they're still hot enough that they radiate brightly in the infrared.

Both stars are visible with the naked eye from a dark sky site, and Fomalhaut should be easily visible even from a urban setting. If you are in Melbourne (or any place at the same latitude), Fomalhaut will be almost directly overhead today soon after sunset — it's bright enough that you can't really miss it. HR 7899 will be a bit harder to find; Pegasus will be visible on the northern sky in the middle of the night, and the Lowell Observatory press release has a diagram that will help you find the right star (it's likely you will need a binocular or small telescope, though).

For more details and images, in addition to the links in the text above, see the (very enthusiastic) Bad Astronomy blog and Centauri Dreams.

Results from the MESSENGER fly-by

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Mercury seen from MESSENGER, 27,000km awayScience data is a little slow in coming from this Tuesday's fly-by of Mercury, but according to NASA everything went as planned and the spacecraft seems to be were it was expected to be. The ground-based antennas are busy handling unexpected problems with Ulysses, another mission exploring that area of the Solar System (it just went over the north pole of the Sun), but we should get more info soon.

Meanwhile, the photo illustrating this article is the first one released by NASA (click on the image to enlarge). It was taken 80 minutes after the closest approach, when MESSENGER was already 27,000km away and looking back. It shows parts of the planet that had never been photographed before (they were not seen by Mariner 10), and that's just the beginning; we can expect many more pictures over the next few weeks, and we can expect to see most of the features of the planet in colour.

Watching Mercury

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Now is a good time to look at that small rock sitting very close to our Sun... Mercury is reaching it maximum eastern elongation, which means that it's about as far away from the Sun (when seen from Earth) as it is going to get this time around. If you have a nice, flat western horizon, look for it soon after the sunset, slightly north of the place where the Sun disappeared. The sky will still be quite bright by the time Mercury sets, but the best day to see it will be on the 21st. For observers in Melbourne, Mercury will set at 21:41 today and 21:42 tomorrow (the Sun sets at 20:45 and 20:44, respectively). For other locations, check this page from the US Naval Observatory.

But, of course, you may prefer to watch it from a better vantage point. If so, now is a very good time: MESSENGER, the first probe to visit that planet since the late 70s, is less than one week away from its first fly-by. The closest approach, at just 200km from the surface, will happen on the 14th, but the cameras will start to take pictures of the planet tomorrow, and some images should be released soon afterwards.

MESSENGER was launched in August 2004 and is in a very complex and long trajectory that will end up with the probe in orbit of the planet... on 18 March 2011. Two more fly-bys happen before then, one in October 2008 and other in September 2009. The reason for this is that it is very hard to send a probe that close to the Sun without having it go into the Sun; it will use its several planetary fly-bys (two of the Earth, two of Venus and three of Mercury) to match its speed to that of Mercury, enabling it to enter the planet's orbit with relative ease.

Recent news

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I haven't been updating this blog much lately... not for the lack of news to comment on, but more for a lack of free time. Now that I'm "back" and, hopefully, with a bit more of free time in the foreseeable future, we'll see more content showing up here. And I'll start with a quick rundown of what's been in the news recently:

Atlantis The shuttle was launched yesterday, finally, and it reached orbit without incident. However, examinations of the thermal protection made in orbit found a 4-inch (10 cm) gap in one of the thermal blankets protecting the underside of the ship. NASA does not seem to be worried about it, as it is not located in any of the areas the suffer most of the heat of re-entry. The shuttle is expected to land on 19 June (Florida time).

Gliese 581c It is not a transiting planet, after all (that is, it never moves between Earth and its star during the orbit). That limits what information can be discovered about this planet in the near future. Still, it looks more and more likely that this planet is not as terrestrial as we'd like it to be; it's more likely that it is more venusian than terrestrial, and the fact that it is tidally locked to its star can't help the weather. Which brings us to...

Gliese 581d This planet received much less attention from the media, but some scientists believe it has a better chance of harbouring life than its more famous brother. Gl581d is significantly farther away from its star (0.25AU, versus 0.073AU for Gl581c), has a longer orbital period (84.4 days) and is more massive (8 Earth-masses). It is also tidally locked to the host star, though. One recent paper argues that a planet of this size is likely to have a dense atmosphere, and certain types of atmosphere would put it safely inside the habitable zone. More relevant still...

Red dwarfs ...stars like Gliese 581 are very, very, very stable after they "mature" (conditions in their vicinity are probably not very friendly during their formative years, though). A planet like Gl581d might stay inside its habitable zone for many billions of years (as opposed to Earth, which will stay habitable for the next billion years or so), which gives it very good chances of eventually developing life. In a "good news, bad news" scenario, though, it is thought that the radiation emitted by the star in its first billion years of life might be strong enough to strip the atmosphere of any planet in the habitable zone without a strong magnetic field, and that any planet in the habitable zone would become tidally locked in its first 500 million years of existence and would lose its magnetic field, thus becoming uninhabitable. We'll have to wait for more advanced instruments to be able to gather more information about what these planets are like today...

New planets There were quite a few; in fact, there were 28 new planets discovered over the last few months. There is a very dense "super-Jupiter" (eight times as massive as Jupiter, but only slightly larger) in a very elliptical orbit around a F-type star (larger and a bit hotter than the Sun) in the constellation Hercules; there was another hot Jupiter in Monoceros, which was interesting mostly because it was the first planet discovered by the European orbiting observatory COROT; another transiting hot Jupiter running a very short (31 hours long) orbit around its host star; a transiting hot Neptune around red dwarf GI-436 (a hot Jupiter is a planet similar to Jupiter — that is, composed mostly of hydrogen — orbiting close to its star; a hot Neptune is similar, but with much more water in its composition); and many more, as exoplanets.org reports.

That's it for now. There are certainly many interesting events going on, and the last few months were very exciting in the field of astronomy; let's hope that the trend continues.

Details on Gliese 581 C

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Trying to get away from the media hype surrounding the announcement of the discovery of the new planet orbiting Gliese 581, I learned that there are some important details that are not mentioned in the popular press.

First of all, there's not much certainty about most of the features that would make this planet habitable (at least, habitable to us). What scientist know for sure, at the moment, is the planet's mass, orbital period and distance from its star. The radius of the planet is pretty much a guess based on assumptions about its density, and the idea that it is a rocky/watery planet comes from the same assumptions. The gravity at the surface depends on the same data, of course.

Also, the surface temperature seems to be a very wild guess. After all, the temperature of a planet depends not only on the amount of energy it receives, but also (and mainly) on how much energy it retains. So, the planet's albedo and its atmosphere density and composition play very important roles, and we know nothing about any of these. The temperature range commonly given (0 to 40°C) assumes an albedo similar to Venus's, and I think we all agree that Venus is not quite habitable. If you assume an atmosphere and albedo similar to Earth's, the average temperature is some -17°C (which is still not terrible, and might allow for liquid water in some locations, but is not very inviting; think Hoth).

One extra point is that the planet is so close to the star that it is almost certainly tidally-locked to it; that is, the same side of the planet faces the star at all times (just like the Moon does in relation to the Earth). What impact this would have on the climate of a planet with a dense atmosphere (if this turns out to be the case) is anyone's guess, but the current consensus seems to be that the effect wouldn't be too bad (winds would probably even out the temperatures). It would be an interesting planet to live in, though, with a sun hovering in the same piece of sky all the time (I guess species evolving in this kind of planet would not have a circadian cycle; I wonder what this would do to the inner workings of brains).

None of this makes the discovery any less interesting and important, but it's always a good idea not to get too excited with the information you see in the media. We may get more information (say, about the size and composition of the planet) when it transits in front of the star as seen from here; the next such event is expected to happen next week. As more people look at this system and more information is gathered, we'll certainly get a clearer picture of what life would be like in Gliese 581 C.

Further reading:

Liquid water on Mars

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Signs of water flow on MarsEarlier this week, NASA announced a press conference for Wednesday morning (US Pacific time; Thursday morning in eastern Australia) with "important news" about Mars. The news are: they have found evidence of liquid water on Mars. The important part is: not in the distant past, but in the last five years.

Two images of the same area of the planet taken by the Mars Global Surveyor in 1999 and 2005 (seen here) show changes that indicate a recent flow of liquid water on the surface; images of a different area show similar activity happening after mid-2002. The supposed flows of water left behind lightly-colored deposits, which are very rare on Mars (disturbances of the soil usually show the darker material that is underneath).

It is presumed that the water flowed from underground deposits, but it's not clear whether the water is permanently liquid (thus providing good conditions for underground habitats for local life-forms) or just becoming liquid for a short period and spurting out of the ground when that happens. When exposed to the thin atmosphere of Mars, liquid water doesn't last very long; it quickly becomes either solid ice (due to the low temperature) or vapour (due to the low pressure).

The Mars Global Surveyor recently stopped sending data and was declared lost, but it clearly brought very important information to Earth; analysis of its images will almost certainly bring more discoveries over the next years. And, of course, the discovery of the presence of liquid water on the planet, even temporarily, brings a boost to the idea of sending people there in the near future.

MRO looks at Opportunity

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Rover Opportunity from aboveThis was posted as one of my "links for the week", but it's cool enough to mention on its own: the new Mars Reconnaissance Orbiter is taking very high resolution images of the martian surface since reaching its final orbit; the pictures show a few centimeters per pixel. That's about as good as the best images of Earth you can see in Google Maps.

And one of the recent images shows rover Opportunity standing by the rim of Victoria crater. The rover is clearly visible, and you can even see the shadow of the camera mast and the tracks it left while getting there. You can see a detail of the image here; click on it to see the full image and the press release.

The ability of seeing the same terrain from two different view points will be very useful to scientists, both in analysing science results and in plotting future movements of the rovers. Come to think of it, it's quite possible that the MRO will be able to find the ill-fated Beagle, the British lander that was lost in late 2003, which may help pin-point the causes of the loss.

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