3D Microscopy of Fossils Embedded in Solid Rock

whitehatlurker writes "UCLA is reporting that a process involving Raman spectroscopy and confocal laser scanning microscopy has enabled researchers to take three dimensional images of fossils that have been embedded in solid stone for over 650 million years. It also permits characterization of the chemical structures of the fossil. As the process is non-destructive and can image microscopic fossils (such as bacteria) with (formerly) soft tissues, there is speculation that this could be used on a mission to Mars to examine sediments there for evidence of life."

Comments

Re:non-destructive

[Anonymous Coward]

This is NOT non-destructive. For CLSM to work you need a sample thin enough to transmit light through it. That means making your sample into a thin section (ie - grinding away EVERYTHING except a few hundred micron thick slice).

Is this new?

[rice0067]

If they are just trying these techniques now, then paleontologists need to start visiting with other departments. The sciences have evolved so much over they last 20 years that in order to do any real work you have to associate with people outside your discipline.

Confocal:

LSCM has been used for ages outside of biology in quality control for chip manufactures.
Laser Scanning Confocal Microscopy improves your Z resolution by eliminating light from above and below the plane of focus. This helps in thick biological samples. Usually you can only image up to 300 microns into a sample (sometimes up to 700 depending on objective and wavelength).
Now, with fossils, I assume that you can only see the very top layer, because light wont penetrate rock that far.

Raman.
The Raman effect was described in 1928. However, robust applications in conjunction with microscopy are somewhat new so I would say that this group is not coming on board to late in the game. Raman with microscopy is pretty cool because you can make chemical maps that correlate to images you have taken. See this paper .

Anyway , I'm glad to see that they are using some advanced techniques.

Re:Is this new?

[Anonymous Coward]

"If they are just trying these techniques now, then paleontologists need to start visiting with other departments. The sciences have evolved so much over they last 20 years that in order to do any real work you have to associate with people outside your discipline."

I could make a joke about paleontologists and geologists moving very slowly, but it wouldn't really apply here.

Actually, this is far from the first work using confocal microscopy on fossils. The article carefully points out that this is the first time it has been applied to fossils this old (i.e. this deep in the Precambrian), which is probably right, but paleontologists have been using confocal microscopy on younger microfossils for years now, though it isn't as commonly applied as it probably could be (e.g., see this article on fossil dinoflagellates and this catalogue of re-imaged type specimens). They've also used serial sectioning techniques for decades, and having access to something 3D is much more versitile than the old way (which was to make a scaled physical model from the information in the slices). Various types of CT scanning techniques are used if the object is big enough. The Raman spectroscopy application is fairly new, but usually ordinary optical mineralogy thin sections provide compositional information. It is only when you want to do a non-destructive technique that it would become important.

"Now, with fossils, I assume that you can only see the very top layer, because light wont penetrate rock that far."

Actually, most of the common minerals involved in fossilization are variably transparent at that scale (quartz, calcite, etc.), sometimes almost crystal clear (no pun intended). Geologists of all types (not only paleontologists) regularly make "thin sections" of rock that are a standard 30 microns thick or so. Also, many organic-walled microfossils are entirely extracted from the rock (like the dinoflagellates mentioned above, or fossil pollen and spores), so you can immerse them in whatever media you like, including standard biological mounting media. Being derived from biological cells, they fall in the same sort of size ranges and are tens to hundreds of microns in size anyway.

Bottom line, confocal microscopy works great for many of them, and as these imaging techniques have progressed, paleontologists have been applying them. I'm sure there are a great many discoveries left to be made as the use of such techniques slowly becomes more pervasive.

Quick Primers

[twitter]

Confocal Microscopy and Raman Spectroscopy. Both have been around for a while and are easy enough to grasp. It's nice to see them used.

Re:Martian meteorites

[Tsar]

The UCLA paleobiologist in question, Dr. J. William Schopf, has already dealt directly with the ALH84001 Mars meteorite controversy:

In "Cradle of Life," Schopf recounts his involvement in evaluating the evidence for life on Mars, and the events that led to the life on Mars NASA press conference. NASA administrators asked him in January 1995 to assess what geologists at the Johnson Spacecraft Center (JSC) in Houston believed might be microfossils in a chunk of a meteorite thought to have come from Mars. The focus was on tiny, orange pancake-shaped globules of carbonate material. The scientists thought these globules might be Martian "protozoans," but Schopf's analysis showed that their guess was wrong.

"Many of the objects merged one into another in a totally nonbiologic way," Schopf says. "Their overall size range also did not fit biology, and they lacked any of the telltale features—pores, tubules, wall layers, spines, chambers, internal structures—that earmark tiny protozoan shells. In addition, the 'lifelike' traits they did possess could be explained by ordinary inorganic processes.

"I raised these points with the JSC scientists. They seemed to agree. I thought the matter was closed. But more than a year later, at the August 1996 news conference, the same little pancakes were again proffered as evidence of Martian life, this time of bacteria rather than protozoans. Evidently the scientists' minds were set—the facts hadn't changed, only the meaning attached to them."

Several weeks before the press conference, NASA again asked Schopf to evaluate the findings. He studied the evidence three times, and was not impressed.

"Crucial questions had not been asked," he writes. "Articles published earlier and critically relevant to the authors' contentions had been ignored. More plausible ways to explain the findings were given short shrift. The claim of 'evidence for primitive life on early Mars' seemed overblown, ill-conceived."

At the press conference, the JSC scientists presented their findings with the aid of "high-tech cartoon videos," says Schopf, who spoke after them.

"I was wearing my best suit—the one I got married in—looking at hundreds of reporters who wanted me to say there was life on Mars," he says. "I had no doubt my words would prove unwelcome. On a scale of one to 10, I gave each piece of their evidence a score. Some, such as the suggested Mars source of the meteorite, I ranked high. But the evidence for life was weak; I gave it a two. A number of scientists later called me to task for being too generous. One Nobel laureate said I should have ranked the evidence zero!

"This attempt failed to find life at Mars. That does not mean Mars contained no life—just that these scientists didn't find any."

How do respected scientists, from Scheuchzer and Beringer to the JSC team, Make such blunders? One answer, Schopf says, is that scientists have the same "strengths, fears and foibles as everyone" and are not so different from our neighbors. They have great successes and, sometimes, great failures. Mostly, "Cradle of Life" addresses one of science's great successes.

Perhaps Dr. Schopf's newer techniques will also be applied to ALH84001 and th