Revealing Rocks on Earth – and Mars

Revealing Rocks on Earth – and Mars

A new UK project could help detect evidence for life on Mars, as well as improve our understanding of how life evolved on Earth.

The project will develop a technique to identify biomolecules in water that have been trapped in rocks for millions to billions of years.

In the proposed technique, rock samples will first be crushed to release tiny volumes of trapped water. Bio-nanotechnology, and specifically SERRS (surface enhanced resonance Raman scattering), will then be used to detect the presence of tiny levels of biomolecules in the water. Biomolecules are organic compounds that originated in a biological (i.e. living) precursor. (Raman imagery is an analytical technique that can map the distribution of a particular chemical throughout a sample. It enables one to compare the location of specific chemical signals to visible shapes within the sample.)

Raman spectroscopy process
The basic process of Raman spectrometry. The mineral sample to be studied is illuminated by a laser beam. Scattered light is collected by the spectrometer. A filter removes any light that is the same color as the laser beam, letting only the light that has changed color (Raman-shifted light) pass through. The diffraction grating separates the light by color (wavelength). The different wavelengths are collected by a charged couple device (CCD) camera. A computer creates a graph showing the intensity of light at each wavlength. Credit: University of Utah, Center of Excellence for Raman Technology.

This technique will provide evidence for the existence and nature of any life that was in the samples when the water became sealed in the rock. The project team will test the technique by using material like DNA, and molecules that represent the remains of bacterial cells.

The project will attempt to access a source of biomolecules that has not been tapped before. A major aim of the project will be to analyze material dating from the time before the Earth’s fossil record became extensive. This could significantly enhance our knowledge of the development of life on Earth.

As well as analyzing samples from Earth, the proposed technique could be used to obtain important information from water sealed within rock samples brought back from Mars. The team also will consider how the technique could be miniaturized for incorporation into spacecraft that travel to other planets.

The technological challenges are at the interface between the physical sciences and engineering, and include microfluidic methods for sample pre-concentration (i.e., the extraction and handling of exceptionally small amounts of fluid), single molecule detection technologies to locate very small amounts of biomaterials, and the elimination of contaminants.

The three-year initiative will be carried out by geologists and bioengineers at the University of Aberdeen and the University of Glasgow, with funding from the UK’s Engineering and Physical Sciences Research Council. The initiative is being led by Dr John Parnell of the University of Aberdeen’s Geology and Petroleum Geology Department, in collaboration with Professor Jonathan Cooper of the University of Glasgow’s Department of Electronics and Electrical Engineering.

"If the technology proves successful, it will enable us to take advantage of a new source of information about the history of life on Earth, and potentially on other planets too," says Parnell.

The Mystery of the Dark Dunes

The south pole of Mars offers one controversial and scientifically appealing region for such Raman scattering, which is proposed for future explorers. Orbital images continues to fuel visual detective work on the waxing and waning of dark ‘colony-like’ blotches recorded by the Mars Orbital Camera. The heated discussion has become known as "the dark dunes" debate.

A recent European Space Agency (ESA) meeting agreed that the seasonal variation in dark and light spots seen on Mars are certainly fascinating. They concluded that the dark dunes might well be worth a detailed look by Mars Express, the European Space Agency’s Mars mission, when it goes into orbit around the Red Planet in late 2003. Agustin Chicarro, ESA project scientist for Mars Express, called the meeting after the spots began fuelling controversy here on Earth in the summer of 2002. "As a geologist, I found the spots quite perplexing and very exciting. I wanted to tap a broad spectrum of expert opinion to decide whether they warrant closer examination by Mars Express," he said.

The controversy began when András Horváth, Tibor Gánti and Eörs Szathmáry from the Planetarium and the Institute for Advanced Study, Budapest, suggested that the spots could be colonies of Martian microbes which wax and wane with the season. The spots appear on dunes found on the floors of craters in the south and north polar regions. The Hungarian team has examined the southern spots in detail. "They appear in late winter and by summer they have disappeared. They appear first at the margins of the dune fields and rarely appear on the ridges of dunes," Szathmary told the meeting.

Their location (which is independent of the elevation of the land) and shape (which is circular on flat surfaces but elongated on slopes) seem to be at odds with a physical explanation alone, say the Hungarian scientists who have proposed a biological explanation instead. A pocket of water, which would normally evaporate instantly in the thin Martian atmosphere, is trapped around them by the overlying ice. As this ice layer thins, the microorganisms show through gray. When it has completely melted, they rapidly desiccate and turn black. This explains why many dark dune spots have a black center surrounded by a gray aureole, say the Hungarian scientists.

mars_viking
The location and shape of the spots is at odds with a physical explanation. (A) Spots develop on the dark dunes rather than on the stony soil nearby. (B) Spots are also ellipsoid in shape or even (C) fan-shaped.
Credit: NASA/JPL/Malin Space Systems/MOC

On the other side of the debate, Michael Malin and Kenneth Edgett, designers of the Mars Orbital Camera on board NASA’s Mars Global Surveyor spacecraft, which recorded the images of the spots, had previously suggested an explanation involving evaporation and re-freezing of predominantly carbon dioxide ice. Their hypothesis is the dark dunes are not biological. The meeting considered these and other possibilities.

What’s Next

Experiments on board Mars Express could help to determine whether the same had happened on Mars. The Mars Express lander, Beagle 2, will touch down on Isidis Planitia, a large plain just north of the equator, at the end of 2003. However, several instruments on the Mars Express orbiter can observe selected areas of the Martian surface at very high resolution.

"If the dark dune spots are selected as targets for analysis, many outstanding questions about the spots could be answered," said Chicarro.

OMEGA, the infrared mapping spectrometer, for example, could determine the mineral composition of the spots, allowing some hypotheses to be eliminated. PFS, the planetary Fourier spectrometer, could measure the amount of carbon dioxide and water ice present, the temperature of the spots compared with their surroundings and the pressure of the local atmosphere. MARSIS, the radar sounder, could determine the thickness of the ice and the HRSC, the camera, could take high-resolution, 3D, full-color images of the spots.

Images and data from orbit may eliminate some hypotheses, but proof of life on Mars will require landers and possibly humans to see the evidence firsthand. A future Mars lander could carry a Raman spectrometer capable of detecting the sorts of pigments used by microbes on Earth to harness solar energy for photosynthesis and to protect them from UV, Wynn-Williams told the meeting. Opportunities to fly this and other innovative instruments to Mars could be provided by Aurora, ESA‘s program of planetary exploration currently under discussion.

Malcolm Fridlund, project scientist for Darwin, an ESA mission to search for life on extrasolar planets, however, ended the meeting on a philosophical note which expressed an understandable sentiment.

"I find it hard to believe," he said "that Martian life, the last vestiges of a fertile time 3.5 billion years ago, has hung on by a thread for all this time until humans have developed the technology to find it."


The three-year initiative will be carried out by geologists and bioengineers at the University of Aberdeen and the University of Glasgow, with funding from the UK’s Engineering and Physical Sciences Research Council. The initiative is being led by Dr John Parnell of the University of Aberdeen’s Geology and Petroleum Geology Department, in collaboration with Professor Jonathan Cooper of the University of Glasgow’s Department of Electronics and Electrical Engineering.

Related Web Pages

Raman Reveals Relics
J. William Schopf’s Cradle of Life
Red Rovers: Returning to Mars
Mars Exploration Website
Two Mars Rover Sites Get Science Stamp of Approval
Evidence for Snow on Mars – and Perhaps an Abode for Life?
Mars Odyssey web site
Ancient Fossils – or Just Plain Rocks?
Extreme Explorers’ Hall of Fame: FIDO