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A picture is worth a hundred words September 28, 2010

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It’s time to make this blog a bit more than just words. I’ve gathered together some pictures relating to ALH84001, hoping this will provide a bit of context and make things easier to imagine.

It’s also relevant because so much of the scientific dispute seems to boil down to interpretations of what people see in the meteorite – a certain feature might look like it’s biological to one person, but appear geological to another.

Here’s the source of it all – ALH84001. Surprisingly small, considering all the fuss it’s generated:

Here are some detailed shots (done mostly with electron microscopes) of the interesting features inside ALH84001. Some of the debate has been about whether these features are actually due to the way the samples are prepared before being imaged by the electron microscope, or whether they are due to bacterial contamination during the thousands of years the meteorite sat in the ice in Antarctica.

And here’s evidence of how much this controversy caught the public’s imagination – it has its own stamp!

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Alternate endings September 27, 2010

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A couple of weeks ago I said that the only way the ALH84001 controversy is going to be settled is by the discovery of more meteorites similar to ALH84001. I was looking at the issue pretty narrowly, thinking about ALH84001 itself as the controversy. If you widen out a bit and think about life on Mars as the controversy, there are plenty of ways that issue could be settled.

The first thing to note is that it’s far easier to prove that there was (or is) life on Mars than it is to prove that there wasn’t (or isn’t).

Here are some of the possible missions to Mars that could shed some light on the issue:

  • A manned mission to Mars – it seems obvious that having a human on the surface of the planet, analysing the rocks and soil, would get to the bottom of this mystery quicker than any other approach.  The question is who can afford to pay for it?
  • A sample return mission to Mars – having a robot return Martian samples to Earth would allow scientists to target specific areas of Mars for study, instead of the arbitrary samples they find in Martian meteorites, and would reduce (but not eliminate) the issues around contamination. There have been sample return missions to the Moon, a comet and an asteroid, but there’s nothing planned for Mars yet.
  • More advanced robotic missions to Mars – the next chance for this is the Mars Science Laboratory mission, launching in late 2011. It’s not really designed to look for life directly, but it will look at things like the chemistry and minerals on the surface to see if they could support life.

If any of these found evidence for life, it would immediately give strength to the ALH84001 claim for life (because the paradigm about Martian life would have changed), or perhaps make the whole dispute irrelevant.

Bill Clinton on ALH84001 September 21, 2010

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Here’s the text of the  statement from President Clinton in August 1996, at the time of the original ALH84001 research:

“Good afternoon. I’m glad to be joined by my science and technology adviser, Dr. Jack Gibbons, to make a few comments about today’s announcement by NASA.

This is the product of years of exploration and months of intensive study by some of the world’s most distinguished scientists. Like all discoveries, this one will and should continue to be reviewed, examined and scrutinized. It must be confirmed by other scientists. But clearly, the fact that something of this magnitude is being explored is another vindication of America’s space program and our continuing support for it, even in these tough financial times. I am determined that the American space program will put it’s full intellectual power and technological prowess behind the search for further evidence of life on Mars.

First, I have asked Administrator Goldin to ensure that this finding is subject to a methodical process of further peer review and validation. Second, I have asked the Vice President to convene at the White House before the end of the year a bipartisan space summit on the future of America’s space program. A significant purpose of this summit will be to discuss how America should pursue answers to the scientific questions raised by this finding. Third, we are committed to the aggressive plan we have put in place for robotic exploration of Mars. America’s next unmanned mission to Mars is scheduled to lift off from the Kennedy Space Center in November. It will be followed by a second mission in December. I should tell you that the first mission is scheduled to land on Mars on July the 4th, 1997 — Independence Day.

It is well worth contemplating how we reached this moment of discovery. More than 4 billion years ago this piece of rock was formed as a part of the original crust of Mars. After billions of years it broke from the surface and began a 16 million year journey through space that would end here on Earth. It arrived in a meteor shower 13,000 years ago. And in 1984 an American scientist on an annual U.S. government mission to search for meteors on Antarctica picked it up and took it to be studied. Appropriately, it was the first rock to be picked up that year — rock number 84001.

Today, rock 84001 speaks to us across all those billions of years and millions of miles. It speaks of the possibility of life. If this discovery is confirmed, it will surely be one of the most stunning insights into our universe that science has ever uncovered. Its implications are as far-reaching and awe-inspiring as can be imagined. Even as it promises answers to some of our oldest questions, it poses still others even more fundamental.

We will continue to listen closely to what it has to say as we continue the search for answers and for knowledge that is as old as humanity itself but essential to our people’s future”.

A couple of things that really struck me about this:

Although there’s plenty of caution in the statement (“this one will and should continue to be reviewed, examined and scrutinized”, “it must be confirmed by other scientists”, and “ensure that this finding is subject to a methodical process of further peer review and validation”), the distinct impression from the end of the statement is that a *big* discovery with profound implications for humankind has just been made.

Secondly, there’s direct link that’s being made between ALH84001 and orders for NASA (and presumably funding) to explore Mars further.

It seems like both of these points served to inflate the controversy – having the president proclaim your research before the paper has been published rubs a lot of people the wrong way, and having a direct link between your research and funding for your organisation make it more difficult for that organisation to question or step back from the controversial findings.

It makes me wonder if things would have turned out differently if the story had been handled differently from Day 1.

Looking for the next ALH84001 September 19, 2010

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I’ve mentioned previously that the only way the ALH84001 controversy is going to be resolved is by finding more Martian meteorites from the same era, and that Antarctica is the most likely place where they might be found. Here are a couple of blogs from people who have been involved in NASA’s Antarctic meteorite search efforts:

http://dawn.jpl.nasa.gov/feature_stories/antarctica.asp

http://www.planetary.org/explore/topics/planetary_analogs/ansmet.html

It sounds like brutally hard work – a team of 6 people spend 6 weeks at a time out in remote areas of Antarctica, and they can find up to 1000 meteorites per season.

NASA is the main player in the search for meteorites in Antarctica, but the Japanese and the Europeans have programs there as well. It would be interesting to see what would happen if a meteorite similar to ALH84001 was found by one of these groups, instead of NASA.

The initial response to the ALH84001 claim September 16, 2010

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The response to the original ALH84001 paper was swift and cautious, at best.

In the same issue of Science as the original paper, there was a news article describing the initial reaction. Clearly the editors of the journal were already aware at this point of how controversial the issue would become. The headline was “Ancient Life on Mars? A meteorite has yielded evidence – but not proof – of ancient life on Mars. The claim has excited skeptical fascination among scientists but has made no converts so far”

In addition to quoting people on both sides of the debate:

“I think it’s very unlikely they have remnants of biological activity,” says William Schopf of the University of California, Los Angeles, who has spent his career separating microfossils of early life on Earth from imposters.

“I’m not convinced,” says interplanetary dust particle specialist Donald Brownlee of the University of Washington, “but I think they have made a credible case that these things could be microfossils. It’s unprecedented. It’s one of the most important things in science, it it’s true. [Exobiology] is intellectually interesting, but without any data, it’s just speculation; I think there’s some data now.”

The article concluded by warning that the issue would not be resolved for some time:

Don’t expect this drama to be wrapped up in the next TV season. The sort of supporting evidence that would convince Schopf and other critics could be slow in coming. As Schopf quoted Cornell exobiologist Carl Sagan: “Extraordinary claims require extraordinary evidence.”

Within a couple of months, the attacks were ramping up.  Edward Anders from the University of Chicago wrote this:

David S McKay et al. deserve praise for discovering possible evidence of past Martian life. The identification of indigenous organic compounds in a Martian meteorite alone is a breakthrough, reopening the possibility of life after the chill cast by Viking. The characterization of the carbonate globules sets a new standard for study of extraterrestrial materials.

After this polite opening, he gets down to the business of attacking the original paper. He concludes with this:

McKay et al. conclude their paper by listing five lines of evidence and then stating:

None of these observations is in itself conclusive for the existence of past life. Although there are alternative explanations for each of these phenomena taken individually, particularly in view of their spatial association, we conclude that they are evidence for primitive life on early Mars.

For all these observation, an inorganic explanation is at least equally plausible, and, by Occam’s Razor, preferable. Consistency arguments alone – weak consistency arguments especially – cannot strengthen, let alone prove, an extraordinary conclusion.

This wasn’t a case where a few strange results appear and are ignored until there’s enough of them that a crisis happens; the controversy existed in its full form right from day 1.

Time for a bit of analysis September 14, 2010

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OK, I’ve spent a bit of time describing the ALH84001 controversy on this blog, now it’s time to start analysing it.

Let’s start with the scientific revolution model. I think it applies pretty clearly in this case. Those claiming that ALH84001 shows signs of Martian life are trying to destroy the existing paradigm (that there is no evidence for Martian life), and if they’re eventually proven right it *will* be a scientific revolution (and a Nobel prize).

I’ll speculate that if that ever happens, people will go back and re-interpret older data from Mars (the Viking experiments and other meteorites, for example) in the context of the new paradigm and discover that they already had evidence for Martian life, but didn’t or couldn’t reach the conclusion because it didn’t fit into the existing (no Martian life) paradigm.

The interesting thing about this controversy is that it’s not completely settled yet. And it’s worth remembering that analysing it in Kuhn’s framework can’t tell you which way it’s going to be resolved!

Who’s the expert? September 9, 2010

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I’ve been thinking back to the discussion we had in class about experts a few weeks ago. And I’m trying to think of who would be an expert on fossilised bacteria in Martian meteorites.

It seems if you use either the “expert at” or “expert about” sense of the word “expert”, you run into trouble. I can think of experts on Mars, experts on Martian meteorites, experts on fossils, experts on bacteria and experts on fossilised bacteria

But how can there be experts on fossilised bacteria in Martian meteorites? No one has ever seen them (ALH84001 dispute notwithstanding), they may not exist at all, and if they do exist there’s no particular reason to believe they would be anything like fossilised bacteria on Earth.

(I’m not trying to criticise the scientists that are working in the field, I just think it’s important to keep in mind that this is a speculative field, or at least one that’s built on a very key assumption – that knowing about life on Earth will help you find life on Mars).

Not the first time September 5, 2010

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ALH84001 wasn’t the start of the debate about life on Mars. I thought it would add some perspective to the debate if we take a brief look at some of the other Martian life controversies:

In 1907, Scientific American published a review of the book “Mars and Its Canals” by the astronomer Percival Lowell. They discuss his findings on vegetation, canals, and ultimately intelligent life on the planet.

I have to admit I wasn’t aware of the extent of Lowell’s Martian research – I thought he just imagined some lines on Mars when looking through his telescope, assumed they were canals and speculated from there. It seems like he was a bit more thorough than that, although it’s sobering to realise how wrong it all is, especially when you read things like:

Prof. Lowell devotes an entire chapter to the photographing of the canals by Lampland in 1903, a feat for which the photographer deserves all praise, inasmuch as it disposes forever of any theory based upon the supposition that the canals are optical illusions induced by eye-strain or the like.

Emphasis mine – it would be enlightening to find those photographs, to see what the whole canal thing was all about, but they seem to have disappeared.

The two Viking landers in 1976 performed experiments to test for the presence of life, but returned negative results. There’s always been a little bit of debate about how conclusive those results really were, and now new research has thrown fresh doubt on them.

The common thread (if there is one) among all these Martian controversies is that there’s some piece of data that can be interpreted several different ways, and the debate is about what’s the most logical way to interpret it. So suggesting that a piece of data supports the idea of life on Mars might not be something that be proven one way or another, but it might not be the most likely interpretation.