Mars Express data show more evidence of past wet climate on Mars

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According to the European Space agency, a recently spotted delta on Mars by the Mars Express is a reminder of Mars' past, wetter climate.

Mars Express is a space exploration mission being conducted by the European Space Agency for exploring the planet Mars.

Mars Express  has spotted the rare case of a crater once filled by a lake, revealed by the presence of a delta. The delta is an ancient fan-shaped deposit of dark sediments, laid down in water.

Mars Express consists of  the Orbiter and  a lander. The latter was designed to perform exobiology and geochemistry research, but failed to land safely on Mars. The lander was named Beagle 2, after the ship in which Charles Darwin sailed when formulating his ideas about evolution.  The Orbiter has been successfully performing scientific measurements since early 2004. 

Holden and Eberswalde craters

Holden crater is 140 km across, filling the left side of the image, while to the right is the remaining part of Eberswalde crater, with a diameter of about 65 km. Credits: ESA/DLR/FU Berlin (G. Neukum)

The delta discovered by the Mars Express is in the Eberswalde crater, in the southern highlands of Mars. According to the space agency report, the 65 km-diameter crater was formed more than 3.7 billion years ago when an asteroid hit the planet.

 A later impact created the 140 km diameter Holden crater. The expulsion of large amounts of material from that impact buried parts of Eberswalde.

  Holden Eberswalde craters in context  

A wider contextual image of the region surrounding Holden and Eberswalde craters. Credits: NASA MGS MOLA Science Team

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

      

Eberswalde crater on Mars formed more than 3.7 billion years ago. The rim of the crater is intact only in the north-eastern part. The rest has been buried by ejecta from the larger, more recent Holden impact crater nearby. Credits: ESA/DLR/FU Berlin (G. Neukum)

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. These secondary sediments, presumably deposited by the wind, were later eroded in the delta area, exposing an inverted relief of the delta structure.

This delta structure, first identified with NASA’s Mars Global Surveyor spacecraft, is characteristic of the presence of a lake in the crater at that time. Such features provide a clear indication that liquid water flowed across the surface of Mars in the planet’s early history.

Source:  European Space Agency (ESA) ; Photo credits: ESA

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