winter

July 16, 2018

Spring is a messy time

In many areas on Earth that get winter snow, spring thaw is a messy time. Frozen ground turns to mud, and there may be runoff everywhere from melting snow and spring rain. Or if you live in a place that […]
May 9, 2018

Entourage

Here’s a grand dune, making its stately way northward under winds blowing mainly from the south-southeast (bottom to top), with a secondary wind blowing from the southwest (lower left to upper right). There are two rippled and sharp-crested slip faces […]
January 8, 2018

Dunes with comet tails

A Piece of Mars: The north polar dunes in this 575×325 m (0.36×0.2 mi) scene are made of dark sand covered by bright winter frost (which will soon sublimate away, as this image was taken in late spring). To the […]
September 5, 2017

Leeward and poleward

A Piece of Mars: The sharp line in this 0.625×0.625 km (0.39×0.39 mi) scene is the crest of a long dune in Mars’ southern hemisphere. The sunlit side is also the lee side: the bright streaks are thin sand avalanches […]
February 21, 2017

Who wins in the fight of wind vs. ice?

A Piece of Mars: This is the crest of one of the largest dunes on Mars (0.5×0.5 km or 0.31×0.31 mi). The wind mostly blows from the right, slowly pushing sand up the windward slope. But frost accumulates on (and […]
September 19, 2016

Light and dark

A Piece of Mars: This 0.96×0.54 km (0.6×0.34 mi) late winter scene is a study in contrast. The dark top half is uniformly rippled. This is the shady surface of the main windward side of one of Mars’ biggest dunes, […]
June 27, 2016

How to hide geology on Mars

A Piece of Mars: Three things are trying to hide in this 0.96×0.48 km (0.6×0.3 mi) scene. 1) Craters are slowly being both scoured and buried by migrating sand, 2) the sand itself is hiding in the lee of crater […]
July 6, 2015

Frosty dunes

A piece of Mars: In this image (0.96×0.54 km or 0.6×0.33 mi), it’s late winter and the sun is barely above the horizon here near the north pole. The dunes are covered in winter frost, most of which is CO2 […]
November 7, 2014

Rivers of freezing gas

A piece of Mars: This 600×450 m (1969×1476 ft) polar scene shows sinuous channels 2-8 m (7-26 ft) wide carved out of ice-filled and ice-covered terrain. They’re not formed by flowing water, but instead by flowing gas that gets trapped […]