Space Topics: Mars Exploration Rovers
The Year in Pictures: 2009
Mired Up to the Hubcaps on Mars
Spirit's "Calypso" panorama (cropped)
Credit: NASA / JPL / Cornell / color mosaic by James Canvin
A higher-resolution version, as well as a VR version, is available at Canvin's
website
|
Having spent 2008 sitting at a steep angle on
the north edge of Home Plate to gather sunlight
through the cold Martian winter, Spirit began
2009 with an attempt to climb back atop the
rocky plateau it’s been studying for almost two
Mars years. The immobile right front wheel
acted like an anchor for Spirit, however, and
the climb was unsuccessful. In February, mission
managers decided to abandon efforts to
climb up Home Plate and instead directed the
rover to embark on a drive counterclockwise
around it. On sol 1,889 (April 26, 2009), as
Spirit was hugging the western slope of Home
Plate, its forward motion suddenly ceased, and
the wheels began digging in. A few subsequent
attempts to move Spirit resulted in further
entrenchment, with five wheels buried up to
their hubcaps—the right front wheel, unable to
rotate, did not bury itself. As Spirit dug in, its
belly may have come into contact with a sharp rock, possibly leaving the rover “high-centered,” which
would make extrication even more difficult. The rest of the summer was spent
studying possible rover extrication methods using a rover mockup at the Jet Propulsion
Laboratory; extrication efforts began in mid-November.
There has been good news:
while in this parking spot, now dubbed “Troy,” Spirit experienced several “cleaning
events” that have
significantly increased its available power. It used that power to perform
science, including gathering a 360-degree panorama from its current position.
In the segment of the panorama shown here, we are looking back at Spirit’s
tracks through West Valley. In the far distance, toward the horizon at left,
are the open plains of Gusev crater, where Spirit landed more than five Earth
years (three Mars years) ago.
The tracks tell the story of Spirit ’s entrapment.
When Spirit got stuck, it was driving backwards, dragging the right front wheel
behind it. At first, Spirit left tracks in the firm soil on the left side of
this view while the dragging wheel created a shallow trench on the right side.
At Point 1 in the annotated image below, the soil began to get looser. At
Point 2, the left-side wheels broke through the firmer surface crust, exposing
softer, brighter (and, it turns out, sulfate-rich) soil underneath. At Point
3, right-side progress slowed as the other five wheels began to dig down. The
frozen right front wheel did not break through and began to act as a pivot,
causing the whole rover to veer to one side. At Point 4, we see the steep walls
of the left-side trench Spirit dug as it sank into the sand. The shape of the
wall was carved partly by the left-side wheels as Spirit steered and attempted
to turn back on course.
(Thanks to Scott Maxwell for the detailed analysis of the tracks.)
Spirit's "Calypso" panorama (annotated)
Credit: NASA / JPL / Cornell / color mosaic by James Canvin
|
|
[ what is this? ]