Chapter 4 of 8

The rocks with nicknames

Sojourner's early rock investigations in July 1997

Told in Pathfinder & Sojourner’s imagined voice · the events are real · source

Sojourner Rover Near The
Pathfinder & SojournerBarnacle Bill. Yogi. Scooby Doo. The rock names were only the beginning.
NASA/JPL
01The team gave memorable nicknames to targets near the lander. Pictures showed where to investigate. The names did not tell anyone which elements the rocks contained; measurements had to answer that question.
A camera could show a rock. Another instrument could investigate its chemistry.
02Sojourner carried an Alpha Proton X-ray Spectrometer, or APXS. It measured elemental composition in rocks and soil. It was not a microphone or a detector that could announce life on Mars.
NASA's Sojourner rover and undeployed ramps onboard the Mars Pathfinder spacecraft can be seen in this image, by the Imager for Mars Pathfinder (IMP) on July 4 (Sol 1).
Pathfinder & SojournerThe rover's wheels also became part of the experiment.
NASA/JPL
03The mission performed wheel technology experiments and tested semi-autonomous hazard avoidance. NASA's contemporary report describes learning about Martian soil as well as the rover's ability to operate around obstacles.
A useful answer needed more than one interesting-looking stone.
04The instruments found differences in rock chemistry. Scientists compared the measurements with images and geological context. NASA's later history describes rocks generally resembling volcanic rocks on Earth—not proof that every Martian rock had the same history.

The big idea

An image, a composition measurement and a terrain observation answer different questions. Together they provide stronger evidence than a nickname or photograph alone.

Think about it

Why could two similar-looking rocks still need separate chemical measurements?

In this chapter: Rover cameras, wheels, hazard avoidance and Alpha Proton X-ray Spectrometer

Sources: Main record · Mars Pathfinder · NASA Science · Mars Pathfinder Concludes Primary Science Mission · NASA/JPL · 8 August 1997

Machine illustration: AI-made. Photos: NASA Image and Video Library, credited on each picture.

Chapter 4 of 8

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