Free Astronomy Magazine March-April 2021

uary 4 and January 25, 2004. The two rovers, each the size of a golf cart, were twins equipped with identical scientific instruments. On Earth, where there is water, there is life. Spirit and Opportunity were sent to Mars to find more clues to that planet's water history and to understand if it could have ever sus- tained life. To do this, the scientists sent the two rovers to two different landing sites on opposite sides of the planet, both of which appeared to have been affected by liquid wa- ter in the distant past. Spirit landed in a location named Gusev Crater, where a lake possibly once existed within the giant impact site. Op- portunity landed in a region called Meridiani Planum , where mineral deposits, particularly hematite, sug- gested that the planet must have had a humid past. The two rovers bounced and rolled on the surface inside of airbag-protected landers. When they stopped, the airbags de- flated and the landers opened. The rovers positioned themselves to take panoramic images that provided sci- entists with the information they needed to select promising geolog- ical targets, useful for telling part of the history of water on Mars. The rovers then began the exploration of those targets and even went far beyond to perform up-close scien- tific investigations. T his image taken by the panoramic camera aboard Opportunity shows the rover's empty lander, the Challenger Memorial Station, at Meridiani Planum. Below, a view captured by the panoramic camera aboard Spirit from a position about halfway between the landing site and the rim of Bonneville Crater. The location is within the transition from the relatively smooth plains to the more rocky and rugged blanket of material ejected from Bonneville by the force of the impact that dug the crater. The panorama spans 360 degrees and consists of images obtained in 78 individual pointings. The Columbia Memo- rial Station lander can be seen about 200 meters (about 650 feet) in the distance by fol- lowing the rover tracks back toward right of center in the mosaic and zooming in. [NASA/JPL-Caltech/Cornell/Arizona State Univ.]