Mars bares big hearts; one rising, one sinking

Erosion has yet to break down this heart-shaped hill.

(CNN) -- A strange mesa really stands out on the red planet on Valentine's Day. So does a pit that extends more than a mile in length.

The heart-shaped landforms are among thousands of bizarre features spied by the Mars Global Surveyor, a NASA satellite that has conducted photo shoots of the planet for more than four years.

The light-colored heart, a mesa in the south polar region, is about 255 meters (279 yards) across, according to NASA.

The presence of the mesa suggests that a layer of brighter material once covered the rougher, darker terrain around it.

This Mars valentine is in the pit.

Another heart, displayed in negative rather than positive relief, is a pit near the Alba Patera volcano in the northern Tharsis plains.

The geologic valentine, created by the peculiar collapse of a walled channel known as a graben, is about 1.4 miles (2.3 km) at its widest, according to Mars scientists.

This week, the Global Surveyor officially started the second year of an extended mission. The robotic workhouse continues to snap great pictures, including one released Monday of the north polar cap.

Mars polar ice cap in photographic study in light and dark.

Often obscured by clouds or seasonal darkness, the cap is the only place known to possess water, the frozen variety, of course. The satellite zoomed in with its camera during a window of clear viewing to snap this picture.

The lower, darker layers seem to possess sizable amounts of sand, unlike the upper, lighter ones, which appear to consist mostly of ice and dust, according to Mars scientists.

Besides checking out points of interest on the surface, the Mars Global Surveyor has begun to keep a close eye on dust storms and cloud systems.

For a weekly Mars weather report, visit the Web site of Malin Space Science Systems, which operates the Global Surveyor camera. The URL is http://www.msss.com/mars_images/moc/weather_reports