MARS TOPICS A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z                    HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site Hellas Planitia The largest impact basin on Mars; it lies in the planet's southern highlands. Hellas Planitia – the roughly circular feature that dominates the image to the right – is about 2300 km (1430 miles) across, or half the size of the United States. It was formed by a giant impact during the late heavy bombardment period of the solar system, some 3.9 billion years ago. Hellas Planitia also contains the lowest elevation point on Mars, reaching about 9 km below the surrounding highlands. The Soviet probe Mars 2 crashed into Hellas Planitia at approx. 45°S 302°W in 1971, thus becoming the first human-made artefact ro reach the Martian surface. Related categories    • MARS TOPICS    • GEOLOGY AND PLANETARY SCIENCE Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP