Mars Exploration Rover

[2] The mission's scientific objective was to search for and characterize a wide range of rocks and soils that hold clues to past water activity on Mars.

On January 21, 2004, the Deep Space Network lost contact with Spirit, for reasons originally thought to be related to a flare shower over Australia.

A delegation of scientists showed pictures and data revealing a stratified pattern and cross bedding in the rocks of the outcrop inside a crater in Meridiani Planum, landing site of MER-B, Opportunity.

Its drivers attempted to drag the dead wheel behind Spirit, but this only worked until reaching an impassable sandy area on the lower slopes.

Drivers directed Spirit to a smaller sloped feature, dubbed "Low Ridge Haven", where it spent the long Martian winter, waiting for spring and increased solar power levels suitable for driving.

[9] In July 2007, during the fourth mission extension, Martian dust storms blocked sunlight to the rovers and threatened the ability of the craft to gather energy through their solar panels, causing engineers to fear that one or both of them might be permanently disabled.

[12] Two months later, Spirit and Opportunity resumed driving after hunkering down during raging dust storms that limited solar power to a level that nearly caused the permanent failure of both rovers.

[13] On October 1, 2007,[14] both Spirit and Opportunity entered their fifth mission extension that extended operations into 2009,[15] allowing the rovers to have spent five years exploring the Martian surface, pending their continued survival.

[21] On January 26, 2010, after six years on Mars, NASA announced that Spirit would be used as a stationary research platform, after several months of unsuccessful attempts to free the rover from soft sand.

[26][27] On March 23, 2015, Opportunity had driven the full 42.2 km (26.2 mi) distance of a marathon, with a finish time of roughly 11 years and 2 months.

[30][31][32][33] The search for evidence of habitability, taphonomy (related to fossils), and organic carbon on the planet Mars was then switched to a primary NASA objective.

It is very similar to the Mars Pathfinder in design and is approximately 2.65 meters (8.7 feet) in diameter and 1.6 m (5.2 ft) tall, including the entry vehicle (see below).

To ensure the spacecraft arrived at Mars in the right place for its landing, two light-weight, aluminium-lined tanks carried about 31 kg (about 68 lb) of hydrazine propellant.

The heat shield was flat and brownish, and protected the lander and rover during entry into the Martian atmosphere and acted as the first aerobrake for the spacecraft.

It carried the parachute and several components used in later stages of entry, descent, and landing, including: Built by Lockheed Martin Space in Denver, Colorado, the aeroshell is made of an aluminium honeycomb structure sandwiched between graphite-epoxy face sheets.

It was specially formulated to react chemically with the Martian atmosphere during entry and carry heat away, leaving a hot wake of gas behind the vehicle.

The slow descent down the metal tape placed the lander in position at the end of another bridle (tether), made of a nearly 20 m (66 ft) long braided Zylon.

The Zylon bridle provides space for airbag deployment, distance from the solid rocket motor exhaust stream, and increased stability.

Connection was important, since it helped abate some of the landing forces by keeping the bag system flexible and responsive to ground pressure.

The base will hold at a level even with the height of the petals resting on rocks, making a straight flat surface throughout the length of the open, flattened lander.

Its power system includes two rechargeable lithium ion batteries weighing 7.15 kg (15.8 lb) each, that provide energy when the sun is not shining, especially at night.

In November 2008, Spirit had overtaken this low-energy record with a production of 89 watt-hours, due to dust storms in the region of Gusev crater.

It produces progressive compression, both lossless and lossy, and incorporates an error-containment scheme to limit the effects of data loss on the deep-space channel.

The Azimuth Drive, mounted directly above the MDD, turned the assembly horizontally a whole revolution with signals transmitted through a rolling tape configuration.

The Jet Propulsion Laboratory maintains a pair of rovers, the Surface System Test-Beds (SSTB) at its location in Pasadena for testing and modeling of situations on Mars.

[66][67][68] Although the Gusev crater appears from orbital images to be a dry lakebed, the observations from the surface show the interior plains mostly filled with debris.

They contain the minerals olivine, pyroxene, plagioclase, and magnetite, and they look like volcanic basalt as they are fine-grained with irregular holes (geologists would say they have vesicles and vugs).

One type of soil, called Paso Robles, from the Columbia Hills, may be an evaporate deposit because it contains large amounts of sulfur, phosphorus, calcium, and iron.

[85] After Spirit stopped working scientists studied old data from the Miniature Thermal Emission Spectrometer, or Mini-TES and confirmed the presence of large amounts of carbonate-rich rocks, which means that regions of the planet may have once harbored water.

The plains of the landing site were characterized by the presence of a large number of small spherules, spherical concretions that were tagged "blueberries" by the science team, which were found both loose on the surface, and also embedded in the rock.