Article Posted on : - Sep 05, 2011

Delta in Eberswalde crater. Photo by ESA/DLR/FU Berlin (G. Neukum).

PARIS (BNS): ESA’s Mars Express has spotted a rare case of a crater once filled by a lake, revealed by the presence of a delta.

The fan-shaped delta is in the Eberswalde crater, in the southern highlands of Mars. The crater was formed more than 3.7 billion years ago when an asteroid hit the planet, ESA said.

The delta covers an area of 115 square kilometres. Small, meandering feeder channels have been spotted towards the top of the crater, which would have filled it to form a lake.

After the deposition of the delta sediments in the crater’s ancient lake, fresher sediments accumulated to cover up a major part of both the channels and the delta, ESA said.

The delta structure, first identified with NASA’s Mars Global Surveyor spacecraft, has provided a clear indication that liquid water flowed across the surface of Mars in the planet’s early history, it added.

The main objective of the Mars Science Laboratory mission is the search for present or previously habitable environments on Mars. ESA’s Mars Express mission has been helping in the search for the best landing site.

Eberswalde was proposed because its delta indicates the long-lasting presence of liquid water in the past and Holden Crater was a candidate because of its mineral diversity and many structures that again suggest past liquid water.

Another candidate, Mawrth Vallis, exposes some of the oldest clay-rich layers on Mars. However, in July, Gale crater, the final entry on the shortlist, was selected as the mission’s landing site, given its high mineral and structural diversity related to water, it said.