Hello, BR.

The only feature that I've questioned and still do is that "impact" crater in Terra Meridiani. Visually, it looks exactly like the one on Earth's Sahara desert, which has been found not to be an impact crater after all.

Mars Global Surveyor
Mars Orbiter Camera

Partially-Exhumed Crater in Northern Terra Meridiani
MGS MOC Release No. MOC2-316, 8 August 2002

The circular feature was once an impact crater. The crater was 2.6 km (1.6 mi) across, about 2.6 times larger than the famous Meteor Crater in northern Arizona. Terra Meridiani, like northern Arizona, is a region of vast exposures of layered sedimentary rock. Like the crater in Arizona, this one was formed by a meteor that impacted a layered rock substrate. Later, this crater was filled and completely buried under more than 100 m (more than 327 ft) of additional layered sediment. The sediment hardened to become rock. Later still, the rock was eroded away---by processes unknown (perhaps wind)---to re-expose the buried crater. The crater today remains mostly filled with sediment, its present rim standing only about 40 m (130 ft) above its surroundings.

http://mars.jpl.nasa.gov/mgs/msss/camera/images/8_2002_releases/bullseye/index.html

- - -

Space shuttle photograph STS37-98-69

Richat Structure, Ouadane, Mauritania

21°04'N, 11°22'W; outer ring diameter: 38 km
Age: unknown

This prominent circular feature in the Sahara desert of Mauritania was initially interpreted as a meteorite impact structure because of its high degree of circularity and multiple ring configuration. Further investigation has shown that the structure probably formed by uplift and erosion of a sequence of sedimentary rocks, creating the series of annular rings, with the harder quartzites of the sequence forming ridges and the softer rocks eroding to form the intervening depressions. Despite thorough investigations, no traces of shock metamorphism or meteoritic signatures have been found at the structure. (Space shuttle photograph STS37-98-69.)

http://www.lpi.usra.edu/publications/slidesets/impacts.html

(I was just at the MGS site today and stopped to take a look at that crater again and here you are posting this... happening a lot lately)