The University of Chicago News Office
June 18, 1997 Press Contact: Steve Koppes
(773) 702-8366

University of Chicago-built instrument will find out what Mars is made of

An instrument designed and built at the University of Chicago and carried on the Mars Pathfinder spacecraft will determine the chemical composition of Martian rocks and soil, a crucial first step in determining what samples, on a future mission, should be brought back to Earth for further study.

Pathfinder, scheduled to land Friday, July 4, will be the first spacecraft to land on Mars since Viking in 1976. The Alpha Proton X-ray Spectrometer is one of the key scientific instruments on board the Pathfinder’s rover, Sojourner, which will be able to roam across the Martian surface guided by scientists and engineers on Earth.

With the mobility provided by the rover and vision provided by a panoramic camera, APXS can be deployed to distant rock outcroppings, providing the first-ever chemical analysis of native Martian rock. The first results from the APXS will be available almost immediately after landing.

B-roll, animation and photos are available from NASA’s Jet Propulsion Laboratory. Live video will be broadcast on the Internet from the Mars Pathfinder control room - visit the University of Chicago’s Web site,

“The basic question we are trying to answer is what is Mars made of?” said Thanasis (Tom) Economou, Senior Scientist in the University’s Enrico Fermi Institute. Economou, along with Anthony Turkevich, the James Franck Distinguished Service Professor Emeritus in Chemistry, designed and built the X-ray spectrometer. The alpha and proton spectrometers (originally designed at the University of Chicago) are being provided by the Max Planck Institut fur Chemie in Germany.

] Parker received his B.S. from Michigan State University in 1948 and his Ph.D. from Caltech in 1951, and joined the Chicago faculty as a Research Associate in 1955. He is the author of three books and well over 300 scientific articles, and has received numerous awards, including the 1989 National Medal of Science and the 1992 Gold Medal of the Royal Astronomical Society. He is a member of the National Academy of Sciences, and from 1983 to 1986 was Chairman of the Academy’s Astronomy Section.

“Down the line we want to be able to find out if life on Mars developed along the same lines as life on Earth, but we won’t be able to answer that question until we can bring back samples to examine in laboratories here on Earth,” said Economou. “Before that can happen, we have to learn as much as we can about Mars and figure out what kinds of samples we should bring back. Our instrument will help select the proper samples for the next mission.”

The APXS can detect any chemical element except hydrogen at concentrations as low as a fraction of one percent. The instrument can detect elements like carbon, nitrogen and oxygen, which are important for life, said Economou, but it cannot determine their molecular structure, which is needed to find out if indeed life ever existed on Mars.

The Sojourner APXS is mounted on a sophisticated mechanism that allows the sensor head to be placed against soil and rock samples in almost any position. Alpha particles bombard the sample, and the spectrometer detects alpha particles, X-rays and protons that are scattered or generated in the sample.

“These studies of Mars will culminate in a sample return mission sometime between 2003 and 2005, which is something we also hope to be involved in,” said Economou.

Turkevich and Economou first developed an alpha proton spectrometer for use on the 1967 and 1968 lunar Surveyor missions (Surveyor V, VI and VII). These instruments, also designed and built by the technical staff at the University of Chicago’s Laboratory for Astrophysics and Space Research, provided the first compete and accurate chemical analysis of the surface of the moon.

The University of Chicago, through its Laboratory for Astrophysics & Space Research, has a long and distinguished history of space exploration. University scientists have participated in more than 35 space missions, including lunar landings, planetary orbiters, and extra-solar missions. John Simpson, the Arthur Holly Compton Distinguished Service Professor Emeritus in the Enrico Fermi Institute, who is still active in space missions, participated in the United States’ first mission to Mars in 1965.
Last modified at 03:50 PM CST on Wednesday, June 14, 2000.

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