MainlyMartian

No methane on Mars

Or at least very, very little. Observations made with the Tunable Laser Spectrometer on Curiosity (paper|press release) rule out an atmospheric level above 1.3 parts per billion with 95% confidence: the data is fully consistent with no methane at all. As the authors say:

Our result greatly reduces the probability of significant methanogenic microbial activity on Mars and recent methane production by serpentinization or from exogenous sources including meteoritic, interplanetary dust and cometary infall.

There will be some background from meteoritic sources, I assume, at the parts per trillion level (where I imagine they will stay undetectible even if Mars passes through the coma of comet C/2013 A1 (Siding Spring)). But these observations leave the idea of a methane-producing cryptic biosphere with no supporting evidence at all. This would feel like the end, if it didn't feel like things had ended a while back -- see this post and links therein. I rather regret that Mars looks deader still than it did before, but I don't regret having been so excited by the subject back in the day -- it's the nature of the game.

My only real loss is that I made a bet on the subject with Chris McKay, right at the beginning of the story, and consequently owe him a meal. But that loss is offset by the far greater gain of, hey, having a meal with Chris McKay. 

And another gain is a greater appreciation of the power of theory. The observational case for methane on Mars was pretty good -- good teams, different techniques. The theoretical case against it, though, as brilliantly articulated by my friends Kevin Zahnle and David Catling and their colleague Richard Freedman in this article (pdf), was really persuasive. That insight has broader applicability, as I noted here:

Thomas Huxley, Darwin's ally in the fight to get evolution accepted, spoke warmly of the facility with which ugly facts can kill beautiful theories. But that fatal ability should not hide the fact that well-applied theories, beautiful and otherwise, can play a crucial role in deciding which observations get treated as facts in the first place. 

 

Organic molecules are interesting but...

So following an NPR piece there's a lot of rumour going round about the possibility that Curiosity has found some organic molecules (Boing Boing, Emily's always excellent Planetary Society blog). If this is indeed the case, then it's interesting but not in itself epoch making. To some extent, since Viking, the surprise had been that there have not been organic materials detected.

As discussed in this post, thousands of tonnes of organic material arrive at the surface of Mars every year. Once it gets there, it either has to be got rid of or it accumulates. Recent work has also shown that most of the Martian meteorites studied have been found to contain organics that were aparently created on Mars through means that have no link to biology (Science paper here). So not only should people presume there are at least some organics on Mars -- people have actually found and studied organics from Mars.

Investigations by Viking and Phoenix did not detect organics, but that is consistent both with processes in the soil destroying them and the protocols used to look for them them being unable to succeed due to the presence of perchlorate (JGR paper here). Curiosity's SAM (Sample Analysis at Mars) instrument suite can look at samples in a wider variety of ways (the sealed cups with chemical solvents may be the key) and is looking at somewhat different environments so if they are there it might well see them.

If that's what's happened its definitely interesting, and I'm sure there will be stuff to be learned from the nature of the organics (for instance, saying if they are made-in-Mars like those in the meteorites or whether they got there from elsewhere). It would be a signal accomplishment. But in the absence of organic molecules that look suspiciously lifelike it would say nothing in itself about the likelihood of life. We don't assume that organics on meteorites mean that the asteroid belt is teeming with life. And it woud hardly be surprising. I certainly don't think it would be historic to discover that a surface on to which organic molecules ceaselessly fall has organic molecules on it.

If you don't believe me, here's someone who actually knows:

What’s the likelihood of finding organics? John Grunsfeld, head of NASA’s Science Mission Directorate, said he likes Curiosity’s chances. “If I had to predict the future, I would say it’s likely."

Look at those cavemen go

Well that was worth getting out of bed for! (I imagine; thanks to the iPad and NASATV I didn't have to bother). I don't think I have much to add to the general yawps of pride, joy, excitement, relief and so on; it was an amazing achievement, and a real thrill. But there's something to be said for taking opportunities to refresh oneself on the basics, which are often forgotten. "It's sometimes a struggle to know what you know," as my friend Ken puts it; as Donald Rumsfeld might have said, there are knowns that sometimes somehow get unknown.

The cost pendulum has swung all the way over. In the days when my Mars interests were at their peak, NASA was in full-on faster-cheaper-better mode. The cheapness carried the can for the loss of the Mars Climate Orbiter, the Mars Polar Lander and the Deep Space Two microprobes. This was not, I think, fully deserved. As I remember the inquiry MCO was lost because of poor management; anomalies were noticed but not hunted down. The MPL case was more complex; more money might have caught the bug that probably did it in. Either way, faster-better-cheaper went out the door. Curiosity has cost roughly 10 times what MPL cost. Rather than being one of a series of landers which, pre-MPL, were intended to fly at every quasi-biennial launch opportunity, it will quite probably be the only Mars lander this decade. 

One ought to assume that the pendulum will now swing back. If you want to continue exploring Mars, you have to find a way to do it cheaper. In practise this probably means do not do it through JPL. JPL, as the world saw this morning, is magnificent. But it is also very expensive. I've talked over the years to various people who have tried to put together cheaper Mars missions. None of them could go through JPL and fit inside budget caps. JPL needs big missions, and fights hard for big missions (cf the saga of SIM). For this reason alone, a Mars lander not conceived at JPL would be a great thing. The "Red Dragon" concept from SpaceX and NASA Ames is obviously of interest here, not least because there's always the chance that if all his other businesses do well Elon might undertake it off his own bat. But other people, such as APL, might also get into the game (I've pretty much given up on ESA as far as this is concerned, but would love to be wrong).

One complicating factor here: longevity. The Curiosity entry, descent and landing (EDL) telemetry came back through Mars Odyssey, which has been in orbit more than ten years. Mars Express and -- amazingly -- Opportunity have been there almost a decade. No one expected that those missions would last that long. If Curiosity can operate interestingly for a decade, then it can basically *be* the program as a big sample return mission slouches towards Bethlehem. 

But redundancy would be better. More missions can drive down mission costs -- for example through the reuse of EDL systems. I have no idea how much of Curiosity's cost went on EDL, but I bet it was a lot. And currently there are no plans to reuse the system at all. Indeed none of the successful EDL systems demonstrated on Mars have ever been re-used after their initial success (the MER systems were meant to be a reuse of the Pathfinder system, but they were so extensively redesigned as to be more or less de novo). Every time people go to Mars they find a new way of doing it. Those who have already succeeded get better at it -- this report by Eric Hand argues that thanks to experience, better knowledge of Mars and better software Curiosity's EDL was a lot less risky than many, including me, assumed. But it would be even easier if the same system were used more than once. And the whole enterprise would be better if people could buy such a system of the shelf, rather than tring to recapitulate the EDL-development expertise that has built up at JPL over decades. 

America still has true interplanetary pre-eminence. Spending billions of dollars, maintaining continuity and inspiring great engineers does bring results, as the EDL success makes clear. I think I heard John Holdren tell someone this morning that no other country had landed on another planet, which isn't quite true; the USSR landed on Venus. Also Europe, with American assistance, landed on Titan, which is pretty planetlike even if it is a satellite, Japan landed on an asteroid, and the USSR landed on the Moon a number of times. But it is definitely true that no other nation has chosen to develop the capability to do things like land Curiosity, or build and operate Curiosity, and it's a pretty open question as to how easily any other nation could. This is much more difficult than simply repeating the feats of the 1960s, as the Chinese space program looks set to do for the next decade. For the time being, the trans-lunar solar system is the province of the United States, with a few allies just about in the game. [Update: This doesn't, though, excuse ignoring international naming conventions.]

There could be fossils. This is, I think, widely downplayed, and probably reasonably. But the odds that Mars once had life are pretty good. Life on Earth started early, and that means both that a) early starts for life on terrestrial planets are plausible, perhaps (depending on how much anthropic principle you feel comfortable with) likely and that b) in its formative years the inner solar system was littered with Earth rocks that had bacteria in them, many of which will have landed on Mars innoculating it through what I (but not enough other people) call transpermia. This is because big impacts knock small rocks off planets, and there were a lot more big impacts early on than there are today. Bacteria can remain viable in space for quite a while, and though the flow of rocks from the surface of the Earth to the surface of Mars would be a lot slower than the flow the other way (it's uphill, not downhill) it would have been appreciable. 

If there was life on Mars, wet sediments from 4 billion years or so ago would be a good place to find fossils of it. Sediments on Mars are likely not to have been anything like as heavily reworked as sediments on Earth are. Microbial colonies can leave quite large macrofossils. Identifying them is not without issues: as the "Knoll criterion" has it, anything being put forward as a fossil must not only look like something that was once alive, it must also not look like anything that can be made by non-biological means. So I don't think fossils are a sure thing, or even likely, and I don't think, if there are fossils, that it will be easy or indeed possible to establish definitively that that's what they are. But my feeling is that the chance of seeing fossils is not that low (in the realm of a few percent more than in the realm of a few chances per million) even if they are not incontrovertibly recognised as such. 

Science won't get people to Mars. In the understandable enthusiasm people are talking of Curiosity as a pioneer for future human exploration. Not so much. Science has never been a driver for human spaceflight. Science was an add-on to Apollo (a great add-on, needless to say) and after that, well, the space station? Really? What's more, sending ever more capable rovers reduces, at the margin, the case for sending scientists (unless, perhaps, they find something both fascinating and flummoxing -- see above). Opportunity and Spirit took months to match the output of a lesiurely few hours of human field geology. Curiosity should be more impressive that way. I'm not remotely saying that there wouldn't be much more for well equipped human scientists to do; just that, at the margin, the case for them shrinks a bit. 

There are, I think, two ways that people get to Mars. One is a big national/international prestige thing for which there is currently no driver. The other is that technology and continued virtual presence on Mars tips the question from "Why go to Mars?" to "Why *not* go to Mars". Wanting to know more about Mars will play, at best, a minor role, though it will benefit hugely from any such endeavour.

[Updated a little to correct some of the typos, lest neophyte blogger Geoff Brumfiel be set a bad example]

 

A little MSL-excitement blogging

I got a lovely email the other day from Leo Enright, friend of this blog, wondering whether it was going to come out of its long hibernation for the MSL landing. Well probably not. I'm not at the landing (having been part of the party for Mars Polar Lander and for Beagle 2 (full archive), I have a suspicion that I'm something of an interplanetary Jonah). And much though I love it, Mars is no longer really part of my beat. But in honour of Leo's request, I thought I'd put a couple of articles from the past few years that are of Martian interest up. Here's one on MSL specifically, and here's one on methane. And if I get carried away in the excitement of this great achievement (or feel the sad need to deliver a post mortem) then -- who knows -- I might even add some fresh stuff. (I won't change the look of the blog: it's going to stay antiquated/charmingly retro).

One thought in passing. It is truly incredible that Curiosity will land while Opportunity is still sending back data. No one would have imagined that possible back in '03. No one. What a triumph.

What blogging I do these days is over at Heliophage, which started off as a blog for my book Eating the Sun (Amazon UK|US). You may find something of interest over there if you're keen on carbon/climate stuff, my idea of nature writing or (my main focus at the moment, away from my day job) geoengineering, among other things.

Other stuff goes on twitter: @eaterofsun

A less alien Mars, a nobler Earth

I wrote this column for Intelligent Life, The Economist's sister magazine, at around the time that MSL/Curiosity took off last year. In setting the scene for the landing, and the new phase of Mars exploration that comes with it, it also serves as a precis and update of some of the thermes of Mapping Mars (Amazon UK|US):

Mars to within a metre

It is a desert plain, caramel-smooth and windswept-empty. To its north rises a mountain taller than Mont Blanc, Mount Rainier or Fuji-san and though, because it is also wider, its sides are less steep and prospects less dramatic, it is still an impressive thing. A massive central shoulder, banded with rocks of different ages, juts out over the plain; to its side, the mountain’s forest-free flanks are cut with canyons. The summit—whittled away by the wind but a stranger to snow—sits farther back, hidden from view. Both plain and mountain are ringed by a wall four kilometres high and almost 500 kilometres long, the rim of a crater the size of Wales. Above the landscape is a washed-out, alien sky. At the right time of year, the Earth hangs over that horizon-rim at twilight, a blueish evening star. 

This is Gale crater, a part of Mars with which some of the inhabitants of that evening star have made an appointment. As this page went to press in late November, a six-wheeled rover called Curiosity was due to be thrown there by a 500-tonne Atlas V rocket. If all goes well—a substantial if, as Mars missions often don’t; a Russian one failed to get beyond Earth’s orbit in early November—then next August a complex system of parachutes and retrorockets will lower the rover through the thin Martian atmosphere to its destination. It will trundle across the plain to the ancient rocks of the mountain’s base and start a slow ascent. It will sniff the air and take samples of rock and soil to analyse in its on-board laboratory. With the help of an orbiting intermediary, it will send back to Earth a torrent of pictures, from the panoramic to the microscopic. 

Curiosity’s climb up that still unnamed mountain [un-named no longer: now it's Mount Sharp Aeolis Mons] promises an extraordinary return in terms of science (and with a price tag of over $2 billion, so it should). It also opens up a new era of exploration—so new, in fact, that it may no longer be exploration at all.

Read the rest here

And here's an archive of all my "Music of science" columns. 

 

The unlikelihood of methane on Mars

One of the early results I think we're expecting from Curiosity is an analysis of trace gases in the Martian atmosphere -- including the level of methane. There was a time when I, and this blog, were obssessed with the news of methane on Mars and what it meant for the likelihood of a cryptic microbial biosphere in the Martian subsurface (full archive). Indeed it is possible, I can't say for sure, that I may have been the origin of the martian-methane-expressed-as-a-number-of-cows meme found recently in an excellent piece by Dick Kerr (summary|paywalled full text). In the excitement, and newly enamoured with the fun of blogging, I was quite the believer.

More recently I have become more sceptical, very largely as a result of this article (pdf) by my friends Kevin Zahnle and David Catling and their colleague Richard Freedman. My take on the article and its arguments, by which i was and remain broadly convinced, appeared a couple of years ago in The Economist. I won't recap it here, but if you're interested it's worth a look. And I liked the conclusion: 

The debate carries a worthwhile scientific lesson in itself. Observations, which to an outsider might sound like simple things, are often remarkably difficult, and depend on complex models to make any sense at all. Thomas Huxley, Darwin's ally in the fight to get evolution accepted, spoke warmly of the facility with which ugly facts can kill beautiful theories. But that fatal ability should not hide the fact that well-applied theories, beautiful and otherwise, can play a crucial role in deciding which observations get treated as facts in the first place.

Pretty soon after landing, insha'Allah, we should know whether the level is in parts per billion or parts per trillion. It may, indeed, be one of the mission's crucial results (unless something satisfies the "Knoll criterion"...)

MSL shakeup -- and a possible methane mission?

The rumours about MSL, mentioned a while back, seem to be getting stronger and stronger. Since the most recent MEPAG meeting a number of people have started more or less assuming that MSL is going to slip back at least one launch opportunity, to 2011; there's also talk of it being doubled up into an MSL A and an MSL B, like MER. It's not been announced yet and may not be a done deal, but the delay, at least, seems very much to be the way that the wind's blowing. It's possible that a formal decision is going to wait until NASA's new administrator, Mike Griffin, weighs in.

An ancillary rumour suggests that if this happens there will be serious consideration given to moving the next Scout opportunity for a small mission up from the 2011 launch opportunity to the 2009 opportunity. Four years is a very short time in which to go from a sheet of paper to a spacecraft, and a truncated selection process might be put in place, in which only the scouts that were shortlisted last time need apply. Those three were: Scim, a mission to pull dust from the upper atmosphere; Ares, an aircraft that would do magnetometry, inter alia; and Marvel, an orbiter with which to measure atmospheric trace gases, including methane, based on the bus for Mars Odyssey. If it were done that way, then the case for Marvel would be extremely strong: the science basis is all the stronger now we have reports of methane, and the technical risk has to be low compared to the other two, since it's a fairly straightforward orbiter, content to look at the atmosphere from above rather than rip through its edges with ramscoops flaring, or extend its wings and try and fly through the stuff. If you wanted to be really practical about the matter, you could save time by just selecting Marvel straight out of the gate -- but I'm not sure that that's actually legal for a scout mission.

Marvel would get really accurate data on methane levels, it would measure any seasonal variations, and it would pick up a bunch of other trace gases if they're there. It would also have a good chance of measuring the carbon-12/carbon-13 ratio in the methane, a measurement which, if it is different from the isotope ratio in the carbon dioxide, would offer strong evidence for a biological source. (The idea is that the methane-making organisms would feed on a well-mixed global reservoir of carbon dioxide, but would discriminate between isotopes as they did so, just as methane makers and photosynthesisers do on the earth; most non-biological processes don’t make such discriminations.) But in an ideal world -- say, for the sake of argument, a world in which the aim was not to fly an already accredited Scout design, but to fly the best methane mission you could -- you'd want to at least consider an alternative mission that looks for the same data a different way.

Marvel would be in an orbit that kept it close to the terminator; its spectrometer, instead of looking straight down, as most spacecraft instruments do, would look at the horizon -- the planet's limb -- in order to see the sun through the atmosphere. This means it gets a strong signal, because it's got a very bright light source shining through a lot of gas. An alternative, which Mike Mumma at Goddard has thought about, is to put a telescope in a halo orbit around the Martian L1 point, which is on a line between Mars and the sun. At L1 a telescope could spend all its time looking at the whole sunlit face of Mars -- and paying attention to any region that was of particular interest.

The challenge of an L1 mission is that the signal is a lot weaker. Your light source is the surface of Mars, which is a lot less bright than the sun. And the light passes through much less of the atmosphere. Light coming to Marvel on a tangent to the planet's surface goes through something like 40 times as much of the atmosphere as light reflected from the surface to the L1 point, and thus the spectral features due to methane, or anything else, will be considerably stronger.

The advantage of L1 is that you could look at specific places -- at resolutions down to a few tens of kilometres -- and look at them at any time of day that you chose. Marvel has to look only at sunsets or dawns, and it can't choose to focus down on a particular region (though it will see all the regions of the planet on a fairly regular basis). If methane levels are strongly variable in space and time, that would seem to be an advantage for the L1 mission. The lower signal at L1 should be something that can be compensated for in principle simply by taking data for longer; in principle, an L1 mission could stare at a particular spot all day.

I really don't know which mission might be better. If I knew for sure that Marvel's signal to noise ratio made it significantly more capable in terms of isotope analysis, I think I'd go with that. There again, the idea of being able to look down wherever and whenever you want is certainly appealing, especially if it were to turn out that there are point sources and complex surface chemistry. But developing a mission from scratch to fly in 2009 would be very, very hard, and I think that the greater amount of design work already done on Marvel would probably trump all other factors. So if there is to be a methane mission at all, it may well be a case of love the one you're with - not too hard, since Marvel is pretty damn loveable.