NASA's Jet Propulsion Laboratory is planning a project to send 16 small landers to the surface of Mars beginning late in this decade, it was announced today.

JPL's planners also were exploring the possibility of a 1996 launch option that would place a small instrumented lander on Mars, possibly with a surface roving vehicle.

Pre-project planning for the 16-lander Mars Environmental Survey (MESUR) mission is underway at JPL. Tony Spear, formerly manager of the Magellan Project, is managing MESUR.

MESUR is the next planned mission to Mars after Mars Observer scheduled for launch later this year, and will complete global reconnaissance of the planet by providing surface measurements at a number of sites that would complement Mars Observer studies.

The mission would send 16 landers in four separate launches to be distributed on the surface to make both short- and long-term measurements of the atmosphere, surface and interior, Spear said.

The short-term measurements include the upper and middle atmosphere during entry, descent and surface imaging, and analysis of soil and rocks for elemental and mineral chemistry.

The long-term measurements include seismometry and weather observations that require simultaneous measurements by the whole network of landers for at least one Martian year (687 Earth days).

The network of instrumented landers would be deployed over three Mars launch opportunities. Four landers would be sent in January 1999 on a single launch vehicle and arrive in December 1999. Four more would go in April 2001 with arrival in January 2002, and the final eight would be launched in May 2003 with arrival in December of the same year.

A dedicated communications orbiter to relay data to Earth would be launched also in 2001. The network would be complete in the year 2003 and the end of the mission would be in 2005. That would require the first four landers to operate for 6 years on the surface of Mars, the second four landers for 4 years and the final eight landers for 2 years.

Spear said evolving technology in microdevices would make it possible to package smaller less-costly instruments and sensors on the landers, and it would be less expensive to send a fleet of small landers than to send one or two large craft.

The 1996 launch option to land a small robotic lander with a rover on the surface of Mars would be a precursor to MESUR, Spear said. The instrumented rover would have a camera and other sensors to look for subsurface water and test the reactivity of the soil.

Instruments on the Viking landers in the late 1970s indicated Martian soil was highly oxidizing, possibly as a result of solar ultraviolet radiation, and might be harmful to organic substances.

The 1996 mission would be a cooperative effort by NASA's Office of Space Science and Applications and the Office of Exploration.

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