UV rays may shed light on Mars life

Upcoming Mars missions will use new method of examining soil for organic compounds

By: Carly Dougher

Posted: 7/2/08

A group of scientists from the United States and the United Kingdom have recently refined an optical method to determine if organic materials can be found in the soils of Mars.
The refined methodology could be used as early as 2009 on a NASA Mars rover, but it is more likely to be implemented on the European Space Agency's ExoMars mission, which will take place in 2013. The goal of both missions will be to look at past and present evidence of life on Mars to be used in further investigation of the planet's habitability.
Dr. Martin Fisk, a professor of marine geology at Oregon State University and co-author of the study published in the American Geophysical Union's journal, Geophysical Research Letters, surmises that if organic matter is found on Mars, then the possibility of life exists.
"Organic matter is the basis of life, and the presence of organic matter on Mars would be a very interesting development," Fisk said. "If there is no organic matter on the surface of Mars, presumably there can't be any life there."
The basic principle behind the science relies on the fluorescence of organic material excited by light at the 375 nanometer wavelength, otherwise known as ultraviolet light. Polycyclic aromatic hydrocarbons, or PAHs, are some of the more common organic molecules in the universe and fall by the ton on planets such as Mars, Venus and even Earth in the form of tiny particles.
When the 1976 Viking probe to Mars did not detect any organic material or PAHs down to the parts-per-million level, scientists were led to believe that the surface was sterilized by gamma rays and UV light.
Dr. Michael Storrie-Lombardi, lead author and director of the Kinohi Institute in Pasadena, Calif., hypothesizes alongside researchers from University College London that organic material is present in Martian soil, but at a depth of one to two meters below the surface.
"Particles fall in from space, hit the surface, and then by wind activity and storms blowing around and covering them up, the particles could be buried down about a meter below the surface and they would survive for long periods of time," Storrie-Lombardi said.
Using this hypothesis, with funding from the National Science Foundation and NASA, the team has developed a system that is simple in design, using the panoramic camera and drill that the European Space Agency already plans to use and simply adding either a UV light-emitting diode (LED) or laser diode as a fixture to the camera. The UV light will be aimed at soil that is brought up from as deep as two meters by the drill and the soil will glow if organic material is present.
Using the UV light as a preliminary measure to find organic material will save chemicals, acids, and stains that the rover must carry in order to conduct more detailed chemical analyses of soil. This is extremely beneficial as there will be limited attempts to run experiments before the onboard resources are used up.
"Even more intriguing is that the UV light can do more then just discover organic material," Storrie-Lobardi said. "The 375-nanometer light also stimulates some of the most common enzymes in biological systems, some of the metabolites in every cell we've ever run across … so if you come across bacteria, algae or lichens, you'd have a chance of lighting these things up."
Tests conducted by Dr. Fisk have shown that a common PAH, Pyrine, lights up with a simple LED, and the scientists are hopeful for similar results whenever their technology makes it to Mars in the coming years.