Tag Archives: superposition

Dunes + Craters = Mars

A Piece of Mars: How do you tell when a planetary landscape shows Mars, instead of Mercury or the Moon or Europa? The easiest way to tell is to look for both craters and dunes, like what's shown here in ...

Mars’ giant sweaters

A Piece of Mars: Sometimes in the floors of small craters, the wind blows in from several directions to produce odd polygon-shaped dunes that look like crochet (maybe Mars is making sweaters for its craters - it is, after all, ...

Steno’s principles, or “how to make sense of pretty landscapes”

A Piece of Mars: Nicholas Steno was a 19th century geologist, who came up with some principles that are still used today to guide interpretation of exposed sedimentary rocks. The principles seem a bit obvious, but then some of the ...

Neverending dust

A Piece of Mars: Some parts of Mars, like this one, are very dusty. This 1.92x1.1 km (1.2x0.67 mi) area has built up a thick deposit of dust that slowly buries the impact craters until they're mere ghosts of the ...

Dune cannibals II

A Piece of Mars: This 0.96x0.54 km (0.60x0.34 mi) scene shows two sets of bedforms (dunes), each aligned in different directions. The more closely-spaced set has sharper crests, and it's superposed on top of (and it is therefore younger than) ...

Windy windows

A Piece of Mars: This 0.96x0.54 km (0.6x0.33 mi) area shows ripples forming on a layer of dark gray material. In a few spots, the gray layer has been eroded away (probably by wind scour), revealing the lighter, tan-colored ...

Is it windblown or not?

A Piece of Mars: This scene is 0.96x0.54 km (0.60x0.34 mi) across. There's an old river valley running across it. The walls of the valley have been eroded and there's a washboard pattern with a wavelength of ~6m (20 ft). ...

Layered winds

A piece of Mars: On the left is high ground, covered with dunes (or maybe they're ripples) running from upper left to lower right. On the right is low ground, covered in deeply eroded dunes (ripples?) running almost from left ...

What is burying what?

A piece of Mars: There's an egg-shaped plateau here (the whole scene is 480x270 m or 525x295 yd across, the "egg" is ~100 m long). It's partly covered by dunes that have extended across it. Or were the dunes there ...

Sometimes I just have no idea

A piece of Mars: The smooth areas are eroded dunes, separated by fields of boulders (the scene is 1.51x1.14 km or 0.93x0.71 mi). The largest boulder near the center is 7.5 m (25 ft) across, the size of a small ...