HiRISE images

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 ❯

Spring is a messy time
Published 7/16/2018 in Lori Fenton's Blog Author lfenton
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 gets winter rains, spring might be the time when mudslides are most common. Spring can be messy on Mars too, although in this case the ice isn't H2O, but CO2. Also, it's not melting, but rather sublimating. But that can still make a big mess. Here's part of a dune field in early spring, located in the high southern latitudes. Normally... read more ❯

Field of barchans
Published 7/8/2018 in Lori Fenton's Blog Author lfenton
It's July, and I've had a busy summer so far. This is my first post in a few weeks - I've been out at various meetings, and last week I spent with my family on vacation. The one week of normal work I had was spent furiously working to help a colleague put together a paper. That left me no time to share pretty pictures with the world. So finally I'm back and able to make another blog post. I decided to make it simple: just a field of pretty barchans. View is 750x500 m (0.47x0.31 mi), HiRISE... read more ❯

The Mars Global Digital Dune Database
Published 5/30/2018 in Lori Fenton's Blog Author lfenton
There are a lot of dune fields on Mars. Over the last ten years I've been part of a group that's mapped out the big dark dunes on the planet to see where they form, and to understand the sedimentary and meteorological processes that control their formation. We compiled a database showing their locations and various physical characteristics. Wait, why do piles of sand form in the first place? On Earth, it's because: 1. There's a lot of sand (not a surprise). 2. There's a lot of strong wind (also not a surprise). 3. The sand is free to be moved by the wind.... read more ❯

Entourage
Published 5/9/2018 in Lori Fenton's Blog Author lfenton
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 on this dune -- can you identify both of them (hint: each wind creates one slip face on the downwind side)?   The dune is ~750 m (2,460 ft) long. It's made of dark sand the wind blows along the ground until it piles up into these big... read more ❯

Wild & dark lacy dunes on twisty bright layers
Published 4/30/2018 in Lori Fenton's Blog Author lfenton
Some windblown dunes on Mars are just beyond words. Take these beasts in this 0.95x0.95 km (0.59x0.59 mi) scene: These are a peculiar type of bedform called a transverse aeolian ridge, or TAR for short, with a spacing of about 50 m (164 ft). Nobody really understands these things: are they dunes or ripples or something totally different? They're common on Mars but unusual (maybe even nonexistent) on Earth. They're also pretty dark-toned here, whereas on most of Mars they tend to be lighter than the surrounding rocks. The TARs mostly cover the surface,... read more ❯

Squish! ????
Published 4/20/2018 in Lori Fenton's Blog Author lfenton
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 ❯

Flow. Lots of flow.
Published 4/16/2018 in Lori Fenton's Blog Author lfenton
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 ❯

Wind-exposed layers
Published 3/26/2018 in Lori Fenton's Blog Author lfenton
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 ❯

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