HiRISE images

Old dunes and new dunes
Published 3/4/2019 in Lori Fenton's Blog Author lfenton
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 dunes around. Most of the dunes preserved in Earth's geological layers are just the bottom fraction of the dunes - the tops were cut off (quite often by other dunes!). That same process has happened on Mars too. But in a few locations, something special has happened: entire dunes have been preserved. That must mean that the dunes formed and then... read more ❯

Why does Lori study dunes on Mars?
Published 2/11/2019 in Lori Fenton's Blog Author lfenton
When I look for something to blog about, I usually go to the HiRISE catalog to see if there are any new pictures that I find interesting. Today this lovely dune field caught my eye: HiRISE images are about 6 km (3.7 mi) across, so that dune field is about 4 km (2.5 mi) wide and 7 km (4.3 mi) long. If you look carefully you'll see that it's a little bit weird. The entire dune field is surrounded by a crisp-edged area of sand that isn't shaped into dunes (I call it an... read more ❯

Wind at the Mars InSight landing site
Published 12/27/2018 in Lori Fenton's Blog Author lfenton
InSight landed in Elysium Planitia on 26 November, 2018, about a month ago as of this writing. Pictures show that it's a flat place, with small scattered rocks lying around. Unlike in Gale crater, where Curiosity is slowly working its way up the side of a 5 km mountain with a spectacular view of the crater rim, InSight's landing spot is a little boring. InSight's view in Elysium Planitia Curiosity's view in Gale crater Image Credit: NASA/JPL-Caltech Image Credit: NASA/JPL-Caltech/MSSS In a way, though, that's interesting, if simply for the contrast between the two sites. Despite this big difference in relief, there is one thing the sites... read more ❯

Pretty little dune field in Noachis Terra
Published 10/8/2018 in Lori Fenton's Blog Author lfenton
Noachis Terra is an ancient terrain on Mars, located in the mid southern highlands. It's the home of many dune fields, big and small. Here's a fairly small one. You can't see it, but this is the floor of an unnamed crater. If you follow the link to the CTX image, you'll see that there's a much larger dune field to the south, trapped in a pit eroded into the floor of the... read more ❯

Complexity
Published 9/24/2018 in Lori Fenton's Blog Author lfenton
Being a geomorphologist and reading a landscape is a little bit like being one of the forensic scientists on CSI (or choose your own favorite investigative show). A Mars geomorphologist usually has to do this entirely by remote sensing. So now imagine that forensic scientist trying to piece together a crime scene by peering at images taken by a drone. On Earth, at least, a geologist can head out to the actual field site and take samples and do some honest labwork to figure out how ancient landscapes formed. Planetary scientists aren't often so lucky (although we do use analog... read more ❯

Ever shifting
Published 9/13/2018 in Lori Fenton's Blog Author lfenton
Dunes are just so amazingly beautiful. I'll never get over how nature can sculpt such regular patterns into endlessly overlapping structures. Here's a small bit of a dune field trapped up high between mountains in the middle of Coprates Chasma. Here I'm not focusing on their setting, but rather the intricate structures of the dunes themselves. The dunes are formed by wind funneling down a narrow valley, headed towards the floor of the much bigger chasma (to the left, far offstage). Here we are in the midst of a dune field, looking at a rippled sandy surface that piles into dunes.... read more ❯

The end of winter
Published 8/28/2018 in Lori Fenton's Blog Author lfenton
Richardson crater is located at 72ºS, about 1000 km (~621 miles) from the south pole of Mars. It's a moderately large crater, about 90 km (56) miles across, and it's mostly filled by one of the biggest dune fields in the southern hemisphere. The dune field has been targeted repeatedly by HiRISE, with a recent count of 83 images. I've probably included images in my blog in the past, but a quick search shows I didn't label them (and I'm far too lazy to go searching). But no matter, since there are plenty of brand new images of the place to... read more ❯

Different sands
Published 8/21/2018 in Lori Fenton's Blog Author lfenton
There's a lot we don't understand about the sediment on Mars. Water, wind, ice, changing temperatures, and volcanic eruptions can all break rocks into grains small enough for the wind to transport. The smallest grains are lofted by the wind, contributing to dust storms, and settling out as fine layers of dust. Slightly larger grains hop (saltate) along the ground and self-organize into beautiful ripples and dunes. Even larger grains (more than a few millimeters in diameter) might be moved by the wind on occasion - these grains are too big to saltate (unless the wind is really strong), but... read more ❯

Where dunes once trod
Published 8/13/2018 in Lori Fenton's Blog Author lfenton
Mars has been dusty, and that's affecting the quality of HiRISE images (just look at the recent images in the catalog and you'll see they're not that great). That's made it hard for me to choose a good one for my blog. I suppose I could go with a grainy image and talk about things like the "cost of real data" and "one person's noise is another person's data" (because surely someone will make use of those poor-quality images to track dust clouds, or something). I'm waiting to see where the bright dust falls out on the surface, because I... read more ❯

Oh, Mars!
Published 8/2/2018 in Lori Fenton's Blog Author lfenton
The HiRISE camera has a website called HiWish that lets anybody (yes, even you!) make image requests. That's right, you can choose any spot on Mars that HiRISE can see, pick any season (or let them pick for you if you don't care), and one day the Mars Reconnaissance Orbiter's path will fly over your spot and, if it isn't scheduled for other observations, HiRISE will take your image! I've made several requests that way. Sometimes I want to get repeat coverage of an area to see if dunes and ripples have migrated - that requires both a "before" and an... read more ❯

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