The Big Dig
|Click image for Mars mole animation. |
Researchers at NASA Ames Research Center in California’s Silicon Valley are adapting the Earth observation instrument for potential use during future Mars missions in a search for water, ice, organics and minerals in the soil. The instrument previously flew over Hawaii in 1997 aboard a remotely piloted, solar-powered airplane, scanning vegetation and land.
"The subsurface on Mars is a very interesting place that needs further study," said Carol Stoker, principal investigator of the project and a NASA Ames scientist. "It is interesting because it’s the most likely environment in which to find life or its organic remnants."
"We are developing an instrument package to observe and analyze martian soil properties down to five meters depth," Stoker said. Called the Mars Underground Mole, the entire system, including sensors, would burrow underground like a mole.
The Mole is shaped like an artillery shell. An internal sliding weight will drive the Mole into the soil. Once dug in, the Mole will connect by a tether to an apparatus on the surface. The tether will include power wires and a fiber optic cable that will transport light collected underground to a spectrometer on the surface above.
|Simulation of Beagle 2 on the martian surface. Beagle 2 planned to burrow underneath the soil.|
Credit: All Rights Reserved Beagle 2
The Mole concept is derived from a device the European Space Agency designed to collect subsurface samples on Mars, according to Stoker.
To enable the Mole to analyze subsurface soils, the NASA team is adding a sensor to the Mole that has been used for more than a decade to obtain spectral imagery of locations on Earth from aircraft.
The instrument, called a Digital Array Scanning Interferometer (DASI), was part of the payload on the remotely piloted, solar-powered Pathfinder aircraft that flew over the Hawaiian islands scanning reefs off the Napali coast, vegetation on Makaha Ridge, the Alakai swamp and agricultural fields.
For a Mars mission, the instrument will be stationed on the planet’s surface, connected to the Mole by a fiber optic cable in the tether. "The fiber optic cable is a ‘light pipe’ that will transport light to the interferometer, which is at the heart of the instrument," said William Hayden Smith at Washington University, St. Louis, who is leading instrument development. "An interferometer measures light interference to precisely determine its spectral properties," he explained.
The spectral images produced by DASI are composed of many different colors ranging from visible to infrared light. Each point of the image has spectra, rainbow-like arrays representing energy and light wavelengths that scientists can analyze. Like a fingerprint or a DNA profile, this ‘spectral data’ from the light reflected from a substance enables scientists to identify it. Researchers say they must be ready to identify possible water, ice, organics and minerals beneath the surface of Mars.
A lamp or laser source will illuminate soil samples through a window in the Mole. The system for collecting light underground and transmitting it to the surface is the primary new development used in the instrument.
|Light pipe for mirror-laser arrangement for martian mole device. Credit: NASA/Ames|
"One advantage of adapting the DASI for a Mars mission is that this instrument can be built very compactly," said Philip Hammer, a scientist at NASA Ames and co-investigator on the project. Because the DASI operates with fixed optics and no moving parts, it also is very stable under severe conditions. The entire Mole will weigh only about 2.2 pounds (1 kilogram) and be about 20 inches (50 centimeters) long.
"We expect to be ready to integrate the DASI instrument with the Mole by the end of 2004," said Stoker. "We will then conduct laboratory and field tests of the system," she added. Laboratory chamber tests designed to simulate potential conditions on Mars will take place at NASA Ames, followed by field tests in Mars analog environments in the California desert on dry lakebeds. Later, tests may take place in permafrost conditions at Haughton Crater on Devon Island, Canada, Stoker said.
The animation starts by looking down at an artist’s rendition of Mars, with a purple hexagon representing a very simplified representation of the "Mars Mole" surface apparatus/rover and lander. The camera zooms down to a side view of the simplified Mars lander. The subsurface is also displayed as a cross section below the lander. A ‘drilling’ mechanism protrudes from the left side of the lander at a 45-degree angle. The driller mechanism pulls up, and at an elbow in the middle, it bends to form a 90-degree angle, allowing the tip to begin boring into the surface of Mars.
The camera zooms out to reveal more of the cross section of the subsurface including various strata. The drilling stops. The camera cuts to the same Mars mole apparatus on the rocky surface of Mars. The hexagon shape of the lander morphs to a rectangular shape and then to a triangular-shaped lander. (This morphing shows that the boring mechanism could be used on a number of different kinds of Mars missions.)
The drilling mechanism again drills from the triangular-shaped lander into the subsurface of Mars, seen in cross section. The camera zooms into the boring apparatus as it descends into the subsurface and goes through layers of rock and soil. The camera cuts to a close-up of subsurface material in the strata. The drill enters the top of the image, and the camera zooms in closer on the Mars mole, which includes a mirror-like surface mounted at a 45-degree angle to the borehole. A laser beam is shown traveling down a ‘light pipe,’ reflecting off of mirror to illuminate soil sample below Mars’ surface. The light pipe also carries resulting spectral data back to instruments on the surface. The camera follows the information flow, up the pipe to the surface apparatus.
Related Web Pages
Five Year Retrospective: Mars Pathfinder
ESA’s Beagle: Sniffing Out Life on Mars
Viking Biology Experiments
Life Beneath the Surface
Spirit’s images and slideshow
Opportunity image gallery and slideshow