X-Ray Instrument for Mars 2020 Rover is PIXL
This illustration depicts the mechanism and conceptual research targets for an instrument named Scanning Habitable Environments with Raman & Luminescence for Organics and Chemicals, or SHERLOC.
Credit: NASA/JPL-Caltech
One of seven instruments selected for a Mars rover that NASA is developing for launch in 2020 would be able to identify chemical elements in target spots as small as a grain of table salt.

PIXL, for Planetary Instrument for X-Ray Lithochemistry, would be mounted at the end of the rover's robotic arm so that it can be placed next to a rock or soil target. It is designed to provide finer-scale identification of elemental composition than ever before possible on Mars.

The instrument's capabilities would help NASA's Mars 2020 rover mission accomplish its goals, which include seeking evidence for past life on Mars.

"If you are looking for signs of ancient life, you want to look at a small scale and get detailed information about chemical elements present," said PIXL Principal Investigator Abigail Allwood of NASA's Jet Propulsion Laboratory, Pasadena, California.

PIXL will be fast. Its intended use is to spend a few seconds to 2 minutes with the instrument's X-ray focused on each spot to be analyzed, then move the beam to another spot, working in a linear or grid pattern to produce a detailed map of the elements in the rock or soil target. The mapped area would be up to about the size of a postage stamp.

The element-identification method is X-ray fluorescence. It reads the X-rays distinctively emitted by various types of atoms when they are excited by X-rays coming from the instrument.

PIXL's design also incorporates a high-resolution camera so that the map of elemental composition can be analyzed in conjunction with visible characteristics of the target area.

"We can correlate fine-scale textures and features with very detailed information about the chemistry," Allwood said. "Understanding these relationships is crucial for investigation goals such as searching for microbial biosignatures."

NASA announced selection of PIXL and six other investigations for the Mars 2020 rover's payload on July 31, 2014.

The Mars 2020 mission will be based on the design of the highly successful Mars Science Laboratory rover, Curiosity, which landed almost two years ago and currently is operating on Mars. The new rover will carry more sophisticated, upgraded hardware and new instruments to conduct geological assessments of the rover's landing site, determine the potential habitability of the environment, and directly search for signs of ancient Martian life.

Scientists will use the Mars 2020 rover to identify and select a collection of rock and soil samples that will be stored for potential return to Earth by a future mission. The Mars 2020 mission is responsive to the science objectives recommended by the National Research Council's 2011 Planetary Science Decadal Survey.

The Mars 2020 rover also will help advance our knowledge of how future human explorers could use natural resources available on the surface of the Red Planet. An ability to live off the Martian land would transform future exploration of the planet. Designers of future human expeditions can use this mission to understand the hazards posed by Martian dust and demonstrate technology to process carbon dioxide from the atmosphere to produce oxygen. These experiments will help engineers learn how to use Martian resources to produce oxygen for human respiration and potentially for use as an oxidizer for rocket fuel.

The California Institute of Technology, Pasadena, manages JPL for NASA.

Guy Webster
Jet Propulsion Laboratory, Pasadena, Calif.

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