Life on Mars? University-created instrument may help find answer

The two identical instruments will soon blast off for Mars on board the U.S. Mars Pathfinder (launch date Dec. 2) and the Russian Mars '96 mission (launch date Nov. 16).

The Mars Pathfinder, the first spacecraft to land on Mars since Viking in 1976, is scheduled to land on July 4, 1997. The key scientific instrument on board Pathfinder's rover, Sojourner, will be the Alpha Proton X-ray Spectrometer (APXS). The X-ray spectrometer was designed and built by Thanasis (Tom) Economou, Senior Research Associate in the Enrico Fermi Institute, and Anthony Turkevich, the James Franck Distinguished Service Professor Emeritus in Chemistry. The alpha and proton spectrometers, originally developed here at the University by Turkevich and Economou for the surveyor Lunar missions in the 1960s, are the contributions of Germany's Max Planck Institut fuer Chemie.

The Sojourner, guided by scientists and engineers on Earth, will be able to roam across the Martian surface. With the mobility provided by the rover and vision provided by a panoramic lander camera, the APXS can be deployed to distant rock outcroppings to provide the first-ever chemical analysis of native Martian rock.

The APXS will also be a key component of the Russian Mars '96 mission, which, although it will be launched two weeks earlier, is scheduled to arrive at Mars two months later than Pathfinder. Mars '96 is a 20-nation collaborative mission that is composed of an orbiting spacecraft, two soft-landing small stations and two penetrators that will dive into the Martian crust. The APXS, deployed on both the soft-landers and penetrators, will measure the chemical composition of the soil at four landing sites.

"The basic question we are trying to answer is, what is Mars made of?" Economou said. "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 samples back to examine in laboratories here on Earth. 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 sites 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 such elements as 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 life ever existed on Mars.

The APXS is mounted on a sophisticated deployment mechanism that allows the sensor head to be placed against soil and rock samples in any position, horizontally or vertically. Alpha particles bombard the sample, and the spectrometer detects the alpha particles, X-rays and protons that are scattered or generated by the sample. From this information received by the spacecraft telemetry, the scientists here can determine the chemical composition of the analyzed Martian soil and rocks.

Mars '96 will be launched Saturday, Nov. 16, from Baikanur, Kazakhstan. Pathfinder will be launched from the Kennedy Space Center on Monday, Dec. 2. Economou will be present at both launches.

"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," Economou said.

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, designed and built by the technical staff at the University's Laboratory for Astrophysics and Space Research, provided the first compete and accurate chemical analysis of the surface of the moon.

Through the Laboratory for Astrophysics & Space Research, the University has a long and distinguished history of space exploration. University scientists have participated in more than 35 space-related projects, including earth orbiting satellites, lunar landers, 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 conducting space-mission experiments, was involved with the United States' first mission to Mars in 1965.

-- Diana Steele