FEATURE
The Methane Mystery
Goddard Invests in New Laser to Detect Gas on Martian Surface
Two years ago, scientists created a buzz when they announced they had detected the presence of small amounts — barely more than 10 parts per billion — of methane gas in the Martian atmosphere. The question was, where did it come from?
Did it emerge from a volcanic eruption? Was the gas carried into the atmosphere by a grazing comet or asteroid or one that hit the surface recently?
Did an inorganic process produce the gas? Or, more tantalizing, did it emerge from beneath the Martian surface from living organisms that produce the gas as a byproduct of their survival?
Although the debate continues, one thing is certain: Scientists won’t be able to answer that question until they locate the methane source on the planet.
Orbiting Laser-Based Absorption Spectrometer
Michael Krainak, head of Goddard’s Laser and Opto-Electrical Branch, hopes his organization will do just that by developing an orbiting laser-based absorption spectrometer that would pinpoint the location and measure the intensity of methane and other trace gases, which could indicate the presence of life beneath the planet’s surface.
Armed with such a global map, planetary scientists could then decide where to land rovers and other scientific instruments to gather in-situ data, which might settle the debate over whether life exists or once existed on Mars.
Laser spectroscopy is a powerful tool for carrying out the mission. When light passes through elements and molecules, specific wavelengths of that light are absorbed and result in a distinct pattern that identifies the molecule.
By tuning laser pulses to specific wavelengths, scientists can target the gas they wish to detect.
Therein lies the beauty of Goddard’s instrument. It’s equipped with an optical parametric oscillator — a device that converts one wavelength to another — and therefore, is tunable in the near- to mid-infrared wavelength bands useful for identifying methane, carbon dioxide, sulfur dioxide, nitrous oxide, and other gases. The laser instrument also offers the added benefit of being able to operate day and night because it doesn’t need sunlight to study absorption features. In essence, it brings its own “sun” to orbit, Krainak said.
| Becoming the Obvious Choice
Since beginning work on the instrument 8 years ago, Krainak says the branch has made good progress. With the Internal Research and Development (IRAD) funding, the branch plans to take laboratory measurements of methane and other gases using a breadboard of its instrument. Successful demonstrations could give Goddard technologists the ammunition they need to attract additional funding and advance the instrument’s technological readiness. The ultimate goal is to make the instrument the obvious choice for future missions.
In addition to Mars exploration, Krainak said the instrument has a wide range of uses on Earth, including global warming studies and medical testing. |
Emily Wilson tests the breadboard of a laser-based absorption spectrometer, which is designed to detect methane and other gases that could indicate the presence of life on Mars.
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