bookofjoe

Circular Sand Dunes on Mars

[An image of almost perfectly circular sand dunes on Mars taken by the HiRISE camera. (Image credit: NASA/JPL-Caltech/UArizona)]

From Space.com:

Strange Circular Sand Dunes on Mars Spotted in NASA Photos

Planetary scientists have captured an image of near-perfectly circular sand dunes on the surface of Mars. While sand dunes across the Red Planet come in a wealth of shapes and sizes, such well-defined circles are unusual.

The slight asymmetry in the sand dunes shows their steep sides are orientated towards the south. The University of Arizona, which operates the High-Resolution Imaging Experiment (HiRise) camera used to take the image, pointed out in a statement that this indicates sands are blown southwards, though the Martian winds may be variable.

The image was taken on November 22, 2022, at a latitude of 42.505 degrees and a longitude of 67.076 degrees. It comes as part of a series of pictures taken by the HiRise camera that orbits Mars on the Mars Reconnaissance Orbiter (MRO) spacecraft.

The collection of images is being used to monitor how frost recedes and melts on the Martian surface as the Red Planet reaches the end of its winter season. While this image appears frost-free, a similar image of the same sand dunes previously taken shows what they looked like while still covered in frost.

The sand dune image was taken while the MRO was at an altitude of around 185 miles (300 kilometers) over the Martian surface. Each pixel in the image represents 25 centimeters (9.8 inches).

This is just one of 60 sites on Mars being monitored by HiRise. The high-resolution camera has been orbiting the Red Planet since the MRO reached Mars in 2006 and began conducting the first dedicated survey of the planet's sand dunes.

Collecting repeated observations of sand dunes over the Martian year (lasting 687 Earth days) has allowed planetary scientists to monitor how fast the dunes move. This has revealed that sand dunes from the equator to the poles are advancing at rates of up to 3.3 feet (1 meter) per Martian year.

[Circular sand dunes on the surface of Mars covered in frost.  (Image credit: NASA/JPL-Caltech/UArizona)]

The camera has recorded a variety of Martian sand dunes with an impressive range of both sizes and shapes, revealing a great deal about weather conditions on the Red Planet. For example, while examining the Lyot Crater in the northern lowlands of Mars in 2010, HiRise imaged dune fields that indicated how local winds are channeled through the topology of this 146-mile-wide (236-kilometer) complex impact crater.

HiRise is also conducting ongoing research that looks at glacier-like formations across Mars and examines the crevasse-type fractures that punctuate their surfaces. By collecting repeated observations over time, the images can help scientists determine the kind of fracture mechanics that occur in so-called "viscous flow features" found at the bases of slopes on Mars. These deposits are believed to have once been rich in ice, but the source of this ice is thus far a mystery, according to NASA.

On December 21, 2010, the primary mission of the MRO ended five years and six months after its launch on August 12, 2005. This new image shows that even 12 years after the end of that mission the contribution to science made by the spacecraft and its HiRise camera is far from over.

Typewriter simulator

I don't know why exactly but this website really makes me smile.

You can too!

Fair warning: there goes the day.

iPad paper-feel screen protectors

Never heard of these until I read Dan Seifert's March 11, 2023 piece in The Verge; it follows.

Apple's iPad and Pencil combination makes for an excellent note-taking or digital drawing solution. But even though writing notes or creating art on the iPad has a lot of advantages over using analog pen and paper, the actual feel of writing with a plastic-tipped stylus on the iPad's smooth glass isn't great. The hard plastic of the stylus hitting the hard glass of the iPad can be noisy, slippery, and just unpleasant to use if you're used to writing on paper.

Yet it doesn't necessarily have to be that way. There is a small cottage industry of paper-feel (or paperlike or paper-type) screen protectors for the iPad that address this issue directly. And as someone who takes handwritten notes on the iPad every single day, I now swear by them.

These kinds of screen protectors have a different purpose than the typical clear plastic screen protector designed to prevent scratches on the screen. They have matte finishes that both diffuse the light coming out of the screen and provide a rougher texture for writing. This has the effect of providing resistance to the tip of the Apple Pencil, which makes writing on the glass feel more like writing on paper and provides more control over your strokes. They also reduce the tapping-on-glass noise you get with the Pencil on the iPad. Writing through the screen protector is no less responsive than without it, and you can still navigate the iPad easily with standard finger taps and swipes.

Common brands of paper-type screen protectors include Paperlike, Moshi (this is what I use on an iPad Mini and an iPad Pro), and PenTips, though there are many off-brand options on Amazon for lower costs. You can find options for every iPad on the market, from the base 9.7-inch model released a couple of years ago to the latest and greatest iPad Pro models. A matte screen protector will typically cost more than a basic clear one, with the name-brand versions running anywhere from $30 to $45 each.

[The matte finish of the screen protector provides texture to the iPad's surface, providing greater control over Pencil strokes]

There are some downsides to be aware of when using a matte screen protector. Because these screen protectors diffuse the light coming out of the screen, there is an impact to the brightness and color saturation of the screen. If you use your iPad outdoors or you primarily use it for watching movies, this might be an issue for you. PenTips’ PenMat offers a clever solution for this: it magnetically attaches to the iPad, so you can easily put it on when you want to write or draw and take it off when you want to watch a movie or get the full brightness of the iPad’s screen. I haven’t used this one myself, but YouTuber Brad Colbow, who creates videos about making art on digital devices, recently tested it and came away impressed.

Those who write with a heavy hand or do a lot of drawing on their iPads might wear out the tip of the Apple Pencil faster with a matte screen protector due to its rougher texture. (This seems to be worst when tilting the Pencil for shading effects.) Replacing the Pencil's tip is easy, and you can get four replacements for less than $20, but it is something to be aware of.

I personally have never had an issue with the reduced brightness and contrast caused by the matte screen protector, so it’s something I leave on my iPad 100 percent of the time. And when I’m writing notes, it’s more comfortable to use, I have greater control, and you can almost read my chicken-scratch handwriting. It also eliminates glare when I’m reading or watching video. One last benefit is the matte screen protector seems to repel fingerprints and other grossness better than the bare glass screen.

If all you use your iPad for is watching video and entertaining young kids, then you probably don't need to spend the money for a good matte screen protector. But if you've had ideas to use it for note-taking or digital art, then it's one of the best accessories you can purchase — once you have a Pencil already, of course. And an iPad with a matte screen protector goes a long way toward providing a similar writing experience to something like a reMarkable 2 while still being capable of all the other things an iPad is great for.