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Hellas Planitia - Wikipedia, the free encyclopedia (366 words) |
 | Hellas Planitia, also known as the Hellas Impact Basin, is a roughly circular impact crater located in the southern hemisphere of the planet Mars. |
| To get an idea of its size, if all the material excavated from it were spread evenly on the continental United States, there would be a 3.5 km (2 miles) thick layer of debris. |
| Due to its size and contrasting light colour, Hellas Planitia was one of the first Martian features discovered from Earth by telescope. |
| Geologic map of the Atalanta Planitia quadrangle (V-4), Venus (499 words) |
| The Atalanta Planitia quadrangle (V-4) is in the northern hemisphere of Venus and extends from 50º to 75º north latitude and from 120º to 180º east longitude. |
| Before the Magellan mission, Atalanta Planitia was known on the basis of Pioneer Venus altimetry to be a lowland area; Venera 15 and 16 radar images showed that it was surrounded by several coronae and coronalike features from the west and by numerous ridge belts parallel to the basin margin to the east. |
| Atalanta Planitia gravity and geoid data show that the lowland is characterized by a -35 mGal gravity anomaly and a -55 m geoid anomaly, centered on eastern Atalanta. |
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