Home Plate is an informal nickname used by NASA scientists to refer to a geological feature on Mars currently under study by the Spirit rover, as of April 2006. It is a rocky outcrop that appears to show layered features. Its name comes from the similarity of its shape with a baseball home plate.

Home Plate is a rocky outcrop about 100 meters across with a flat-topped shape; from above, it looks vaguely pentagonal. It is located within the huge Gusev crater, just south of Husband Hill.

The feature is interesting to scientists because of its layered appearance. Spirit's twin, Opportunity, currently studying sites on the opposite side of the planet, has discovered numerous layered rocks, but Home Plate is the first example to be found at Spirit's site. It bears a striking similarity to Burns Cliff, a feature studied by Opportunity at Endurance crater.

Spirit arrived at Home Plate on sol 744 (February 7, 2006) and has completed a scientific investigation with her robotic arm before moving to Low Ridge Haven due to power concerns. She returned on sol 1126 to resume those studies.

Spirit is due to spend her third Martian winter on Home Plate's north edge.

Origins

Scientists now believe that Home Plate is an explosive volcanic deposit. It is surrounded by deposits of basalt, which exploded on contact with water. The presence of brine is further supported by the high concentration of chloride ions in the surrounding rocks. The presence of bomb sags (laminae typically found in beds of volcanish ash) seems to confirm this hypothesis.

A patch of 90% pure opaline silicon dioxide was unearthed by Spirit in the vicinity of Home Plate. The patch is believed to be formed in acidic hydrothermal conditions, which supports the theory that Home Plate is of a explosive volcanic origin. Water is also present as mineral hydrates.

References

External links

• Nasa's Mars Exploration Program
• Current position of the Mars rovers - Home Plate is visible, with Spirit's journey around it.
• www.marsgeo.com The Geology of Home Plate
• The Planetary Society Weblog: Home, Sweet Home for Spirit
• Official Mars Rovers site

See also

• List of rocks on Mars