March 4, 2019

Old dunes and new dunes

On Earth, really old windblown dunes don’t usually survive long enough to become part of the geologic rock record. Dunes are made of unconsolidated sand, which is easily eroded by just about anything, so it takes special circumstances to keep […]
October 18, 2018

The martian wind is a geologist

Right now, the Fourth Landing Site Workshop for the Mars 2020 rover mission is happening. It’s the last one, and in a few hours the scientists attending the workshop will vote on which of four sites they think the rover […]
April 30, 2018

Wild & dark lacy dunes on twisty bright layers

Some windblown dunes on Mars are just beyond words. Take these beasts in this 0.95×0.95 km (0.59×0.59 mi) scene: These are a peculiar type of bedform called a transverse aeolian ridge, or TAR for short, with a spacing of about […]
April 23, 2018

Reusing old canvases

The wind on Mars is an artist, or at least it tries really hard to be one. It flutters up and down mountains, winding along valleys, dragging its wings in the sand and building up really amazing structures that could […]
April 16, 2018

Flow. Lots of flow.

Over the years, many things have flowed across the surface of Mars: lava, ice, water, and wind. Two things have flowed in this image (the view is 0.75×0.6 km or 0.47×0.37 mi): Image credit: HiRISE ESP_026541_1840, NASA/JPL/Univ. of Arizona If […]
March 12, 2018

Wind on Mars and the Huygens-Fresnel Principle

How about some basic physics? It’ll be easy, I promise. Just look at the pretty picture below (click on it to see it better): The big crater is ~400 m (1/4 mile) across. Wind blows sediment from the top to […]
February 12, 2018

Where dune fields begin

This is the upwind edge of a dune field (825×625 m, 0.51×0.39 mi). Winds blow down a cliff (offscreen) from the lower right, blowing sand toward the upper left. Elongated dunes have formed parallel to the resultant wind direction, only […]
January 22, 2018

Arnus Vallis, Mars

A Piece of Mars: This is a section of Arnus Vallis (scene is 1.25×1 km, 0.78×0.62 mi). It’s a >300 km long valley that was carved out, not by water, but by lava, long ago. Since then the wind has […]
January 2, 2018

Fuzzy dunes

A Piece of Mars: The dunes (or maybe they’re ripples) in this valley appear to be fuzzy (the view is 625×775 m, 0.39×0.48 mi). They’re not really fuzzy, but it’s not actually clear what’s going on. They seem to have […]