"Hey, how'd that get there?"
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During the first day of science operations, or sol 7 of the
mission, a "mystery boulder" created some confusion and much
discussion among the scientists. The rock, named Woodstock,
seemed out of place at the landing site based on its dark,
heavily "varnished" surface, its texture, and its mineralogy,
which was determined from spectral measurements. It appeared to
be a basalt, the kind of rock produced by volcanic eruptions, but
there were no obvious volcanic landforms nearby, and no other
obvious basaltic rocks. "We actually joked that the FIDO field
team had planted it next to the rover to confuse us," scientist
Steve Ruff said with a laugh. The FIDO field team is a group of
engineers who are caring for the FIDO rover in its desert
location.
Anticipating that this rock must have originated from somewhere
nearby, several of the scientists began to use satellite images
acquired prior to the mission to look for a location in the
landing ellipse that included a volcanic landform and the kind of
cliffs at the landing site that are seen through the rover's
cameras. The landing ellipse is an area roughly 120 km (70
miles) long and 30 km (18 miles) wide that represents the region
in which the spacecraft can be predicted to land with a 99% level
of confidence. It's often tough to match up orbital and ground
images to determine the exact rover landing spot in an area of
that size, but that's one of the first jobs the science team will
tackle when the Mars Exploration Rovers arrive on Mars.
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Steve Ruff |
For determining FIDO's position, the only possible place that
combined volcanic and cliff landforms was well away from the
center of the ellipse. "This location was not unreasonable, but
many of us had assumed that the rover had 'landed' closer to the
center," commented Ruff. Then today, on sol 10 of the mission,
scientists received a confirmed answer on the location of the
rover using a long-awaited, newly arrived data set. The rover
actually was nearer to the volcanic landforms and cliffs than
previously assumed before discovering Woodstock.
The radio transmissions between the rover and the command center
can actually be used to help locate the position of the rover.
By sol 10, the processing of those radio data provided an
accurate position for the rover, answering more precisely the
question "Where are we in the ellipse?" But clues to that answer
started to appear the day before, with the observation of a
seemingly out-of-place rock and some clever detective work by the
science team.