Tag: engineering

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Cool image time! The picture to the right, cropped, reduced, and enhanced to post here, was taken on October 2, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).

The science team labeled this a “lava margin.” The darker material on the right is apparently a newer deposit of lava, flowing on top of the lighter lava on the left. The newer deposit is only about three feet thick, so it had to have flowed fast almost like water to cover this large area with such a thin layer before freezing. Even so, this new lava layer has a roughness greater than the older layer below it. Either the older layer is smoother because of erosion from wind over eons, or the lava in these two layers was comprised of slightly different materials that froze with different textures.

The small ridges appear to be wrinkle ridges, created when material shrinks as it freezes.

This margin marks the edge of a very large flood lava event, as illustrated by the overview map below.
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Cool image time! The picture to the right, cropped to post here, was taken on December 29, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows strange spidery formations on the rim of a 17-mile-wide crater about 500 miles from the south pole of Mars.

Scientists think these spider features are formed due to the seasonal cycle on Mars. In the winter at the poles the carbon dioxide in the atmosphere falls as snow in the polar regions, creating a thin dry ice mantle that covers everything. When spring arrives, sunlight goes through the clear mantle to heat its base, causing that dry ice to sublimate into gas that is trapped below the mantle. Eventually that mantle cracks at a weak point and the gas escapes, spewing dark dust on its top. By summer the mantle is entirely gone, and the black splotches disappear as they blend back into the same colored ground.

At the south pole the ground appears to be firmer and more structurally sound than at the north pole. The trapped gas appears to travel upward along the same tributary paths to the same escape points each year, thus carving these spidery features that are permanent features.
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Cool image time! The picture to the right, cropped to post here, was taken on December 20, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the science team labels as “Dunes with Blotches.”

The blotches, or as I call them splotches, are the round dark patches on dunes themselves. Though their darkness is reminiscent of the dark patches that appear as spider features in the south polar regions of Mars, there are problems linking the two. The spiders form when the winter mantle of dry ice that falls as snow begins to weaken when the Sun reappears in the spring. Sunlight travels through the clear dry ice to warm the base of the mantle, causing it to sublimate into carbon dioxide gas. That gas however is trapped at the base, and only escapes when the thin mantle cracks at weak points. As the gas puffs out it carries with it dust, which leaves dark patches on the surface that disappear when the mantle disappears entirely by summer.

In the southern hemisphere at the poles the ground is somewhat stable, so the trapped gas appears to travel along the same paths each year to the same weak spots. This in turn causes it to carve spidery patterns in the ground, like river tributaries, except here the tributaries of gas flow uphill to their escape point. At the north pole the ground is not as stable. Instead we have many dunes, so that the dry ice mantle sublimates away at different places each year. There is no chance to form such spider patterns over time.

Making these splotches more puzzling is the season. This picture was taken in the winter, at a time one would think no dry ice is sublimating away.
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Cool image time! The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on September 27, 2023 by the high resolution camera on Mars Reconniassance Orbiter (MRO). Dubbed a “terrain sample” by the science team, this picture was likely chosen not as part of any specific research project but to fill a gap in the camera schedule so as to maintain that camera’s proper temperature.

When the team needs to do this they try to pick interesting targets. In this case the location is the region of many many parallel north-south fissures that extend for more than 800 miles south of the giant but relative flat shield volcano Alba Mons. These fissures are grabens, cracks formed when underground pressure pushed the ground up and caused it to spread and crack.

What attracted me to this picture is the ridgeline. It struck me as a wonderful place to hike. I have even indicated in red the likely route any trail-maker would pick to go from the valley below up onto the ridge, and then along its knifelike edge to the south. The height of the cliff down to the east valley averages about six hundred feet, guaranteeing beautiful scenery the entire length.
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Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken on December 21, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The science team labeled it a “fresh crater”, but that description I think is misleading, as it implies a recent impact.

The crater does not look like a fresh impact crater to me. Such things on Mars usually appear very dark, as the impact dredges up dark material. This crater is not dark. More significant is the crater itself. The small 300-foot-wide inner crater, surrounded by a circular plateau and all sitting inside the larger 1,200-foot-wide crater is completely unique compared to any impact crater I have ever seen. Impacts in soft material, such as ice-impregnated ground, can cause concentric ripple rings, but they don’t look like this.

Instead, this crater more resembles the caldera of a volcano, where subsequent eruptions can produce overlapping depressions at the volcano peak. (See for example this picture of Olympus Mons.)

Moreover, the crater sits on top of a peak approximately 300 feet high. While impacts in ice-impregnated ground on Mars can produce splash aprons as seen here, the crater usually sits at about the same elevation as the surrounding terrain, not at the top of a peak. This peak suggests the apron was forned not by a splash but repeated flows coming down from the top.
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