HiRISE images

This isn't a full blog post. Just something I saw while looking around for other things on Mars. And for once it's (probably) not related to the wind. But it's cool enough to share. I saw something that went "squish" ???? . This is a ~1.2 km (0.75 mi) wide crater in the northern mid-latitudes of Mars. I don't know much about this region geologically (haven't done my homework, as this is just a quick look). This crater has a set of layers in it that have partially eroded away. And underneath those layers on the crater floor are what look like... read more ❯

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 0.75x0.6 km or 0.47x0.37 mi): Image credit: HiRISE ESP_026541_1840, NASA/JPL/Univ. of Arizona If you know my blog at all, then you might recognize the big structures as yardangs. They are part of an enormous set of yardangs on Mars called the Medusa Fossae Formation. At some point in the past, probably a few billion years ago, the wind kicked up a bunch of sand that carved out these structures, blowing from the lower left to... read more ❯

On Earth, layers comprising the geological record of an area are most often exposed by fluvial erosion, as a river cuts through rock (a typical example is the Grand Canyon). On Mars, fluvial channels are not so common (especially in the past few billion years). But the wind has relentlessly worked away at the surface, sometimes revealing strata laid down long ago. Click on the image for more detail. This is a tiny bit (0.5x0.375 km, or 0.31x0.23 mi) of the side of an "Interior Layered Deposit" in the middle of Candor Chasma, called Juventae Mensa. Wind blowing from the upper... read more ❯

A few weeks ago I wrote about dunes leaving behind trails near the north pole of Mars. They do this in a few other places as well, but it's not very common. Below is a rare example, this time on the floor of Hebes Chasma (one of the Valles Marineris), which is a tectonically-opened hole in the ground that's about 6 km deep. I don't mean to repeat the same topic, but geologists are usually drawn to terrain that so plainly lays out the geological story of an area, and obvious dune-generated layers are pretty rare. (Also pretty.) (HiRISE ESP_045586_1585, NASA/JPL/Univ.... read more ❯

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 the bottom of the view, making some dune-like features (TARs, really) at the top and inside the crater. The rim at the top of the crater has a set of hills with a dip inbetween them, which allows wind and sediment to be funneled into the crater through a narrow valley.... read more ❯

Baby dunes on Mars are pretty big compared to those on Earth. In this 885x512 m (0.55x0.32 mi) frame, there are four dunes of roughly the same size, all of which are about as small as dunes can get on Mars. They're ~180 m (590 ft) across, several times bigger than similar "elementary" dunes on Earth. There's another key difference between Earth and Mars dunes. The avalanching lee slope (the slip face) comes to a point in these dunes. That's because there are two winds forming these dunes, one from the upper right and one from the upper left. On Earth,... read more ❯

There's so much going on in this 0.75x0.75 km (0.47x0.47 mi) image. You're looking at a broad dune migrating toward the upper right. It's early summer, but this is close enough to the north pole that some winter ice lingers (pale blueish white), amid slumps that have shed down from the dune. The slumps probably form as ice weighs down the dune sand -- they are not seen on dunes at lower latitudes, where ice is less common. The upwind side of the dune is interesting as well. The dark dune slowly migrates forward, leaving behind bits of itself (sort of... read more ❯

Many dunes on Mars are actively migrating, like these dunes (view is 0.4x0.5 km, 0.25x0.31 mi). These are found deep in Ius Chasma, one of the Valles Marineris. These dunes slowly migrate toward the right, pushed by winds blowing from the lower and upper left.       Comparing this recent image with the first HiRISE image taken ~10.5 years ago (that's ~4.4 Mars years) shows development of a crest linking these two dunes, indicating the wind from the upper left has been most active over the last few years. Click on the grayscale image to the left to see an animation of this... read more ❯

This is the upwind edge of a dune field (825x625 m, 0.51x0.39 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 avalanching into slip faces once enough sand has piled up (there are two slip faces at the upper left). The tan/black mottling shows where tan dust has settled or been removed from the dark sand by recent winds. Large grains are heavier and harder for the wind to move, so they form into ripples (with a 10 m or... read more ❯

The busy, busy wind has moved a lot of things to make this 0.6x0.85 km (0.37x0.53 mi) landscape. First it built a big dark dune, covering it and the surrounding surface with ripples. Then it dumped a bunch of bright yellow dust all over everything, maybe the result of a nearby dust storm, or maybe just gradual fallout in a quiet season. And then it made some whirlwinds into dust devils that scribbled away some of the dust, revealing the dark dune surface. (I'll also note that when turned upside down, this looks like an interesting one-shoulder dress with a... read more ❯