# Tag Info

44

Actually, most of the surface of the Moon is covered with craters like that. The exception are the large dark 'seas', which are in fact basaltic plains. The seas are mostly present on this side of the moon; the far side of the moon is almost entirely composed of craters. The reason you see a ring near the terminator (the boundary between the illuminated and ...

41

Aside from the excellent points made in James K's answer, there are other ways to date craters. For example, when the rays of one crater overlay those of another, we know that the former is younger than the latter. We can also estimate ages of large craters by counting subsequent craters inside the crater floor. Crater counting is one of the more common ...

24

The "weathering" processes are very slow compared to those on Earth. They are caused by the impact of micro-meteorites and the effect of the solar wind and cosmic radiation on the surface. The solar wind tends to darken the moon minerals. This is why the younger craters have bright rays and the older craters appear much darker. There are a number of ...

12

I looked at the image and annotated it based on what it most likely is: In black is the formation itself. In blue is a depression underneath it. In grey is part of the boundary of what you believed to be the disappeared half. In green is a ridge to the north. In red are several craters. Here's a more likely hypothesis for what this actually is. The ...

10

I was on the targeting team for one of the cameras that discovered most of these new impact craters. The reason for the distribution is simply because it's easiest to find "new" impact craters in the dusty regions of Mars. Often what we see is the dark-toned blast zone created by the impact in lower-resolution data, which has a large areal footprint. Then, ...

6

It is just a rock. A complex crater like Tycho is formed in several stages as the rock behaves like a fluid. The initial impact completely destroys the impactor and excavates a large cavity in the moon, and ejecta is shot out to all sides. Powerful shock waves push the rock to the side building large walls. As these push down on the edges of the crater, ...

5

The simplest explanation for the latitudinal distribution would be that most small solar system bodies that could impact one of the planets happen to orbit near the ecliptic plane and Mars' orbital inclination is only ~$1.85^{\circ}$. The longitudinal "clumpiness" may be due to erosion rate differences, since the new impacts almost exclusively appear in the ...

5

Nice picture! Those peaks are actually a very common feature in craters formed by large impacts. Craters with these features are known as "complex craters". Basically what happens is that when the meteor hits, it pushes in the surface. Then the underlying mantle produces an "elastic rebound" and pushes outwards. This is a similar effect to what happens when ...

4

Jezero crater is roughly 50 km across, and it is emplaced within the wall of Isidis crater ("basin"). Isidis itself has seen a lot of erosion, but it has been dated by lots of different people through the use of superposed crater counts (craters on top of it, with the number-age relationship tied to the Moon) to somewhere around 3.85–4.05 billion ...

4

That is the rebound effect. Just like a rock falling into a pond causes a big ripple and a big drop to jump out in the center, the same happens with a rock striking the Moon. Refer to this astrophysics stackexchange for more information.

4

The occur all over the world. On this image each yellow circle is an recent impact of a small asteroid the size of the circle is related to the energy of the fireball (the sizes of the circles don't represent crater areas). You will note that there is no region that get more impacts, and similarly, nowhere is safe. The very large yellow circle is the ...

4

Asteroids come in all shapes and sizes, and generally the bigger they are the easier they are to detect. Small asteroids, from a the size of sand grains (properly called meteoroids) to a few meters across hit the Earth everyday without causing harm and are undetectable until they hit (we call the trace as they hit the atmosphere a meteor) They cause no ...

4

Yes, there is an observed impact of a comet into a celestial body. A fairly recent one in 1994 is the comet which impacted into Jupiter, Shoemaker-Levy-9 Here's a video of this event happening.

4

One criterion that works well is the presence or absence of smaller craters inside. If the crater is clean, it's probably new. If it's full of smaller craters, it's old. This applies to planets and satellites with no atmosphere, or with a rarefied atmosphere.

3

Asteroid impacts on the Moon are monitored by researchers and amateurs. The Meteoroid Environment Office has a list of candidate impacts I stumbled upon, Lunar Monitoring Program is another. Videos and photos of Lunar impacts. One impact photo to the left. All recorded impacts 2005-2015 to the right above.

3

Theoretically, if you're talking crater to planet size, I (think) a crater that covers half or a bit more than half of the planet is possible if you have a dense planet (Say, Mercury) and a lighter, more icy object (say, Titan). Mercury would break Titan apart like a hammer hitting glass (er, maybe), but Titan, which is slightly larger than Mercury but ...

2

It seems not yet. The non-uniform density of craters seen on Ceres is still under investigation. From the abstracts of those papers, they're still working on trying to date the ejecta material from that crater, and trying to understand the resurfacing that appears to be going on.

2

All three. The impact velocity will be huge and the kinetic energy of astroid extremely large. The asteroid will be pulverized into millions of fragments of asteroid. Many of these will be as small as dust particles and will be vaporized from the heat associated with collision. Hence some small fragments will evaporate will other larger fragments will be ...

2

I found a partial answer in this article on the smaller and younger Giordano Bruno crater. The impact creating the 22-km-wide crater would have kicked up 10 million tons of debris, triggering a week-long, blizzard-like meteor storm on Earth... So the secondary effects of the Tycho impact would have been even more spectacular. However, I don't know ...

2

The German Wikipedia Article states that the Jezero crater lake (note: this only referres to the lake, not the crater itself!) is estimated to have existed around 4 billion years ago. In the English version, it is said that the delta may have required a period of $10^6–10^7$ years to form This means that the crater must have existed for at least around 4....

1

I guess the point is that there are two ways to calculate how big a crater a given impact will create. One is based on calculating how much rock the impact energy can shatter so the main constraint is the strength of the rock) the other on calculating how much it can lift (so the main constraint is the weight of the rock). For small impacts the first is the ...

1

Most lunar craters are too small to resolve with the naked eye; I would measure a published photograph. A crater near the limb appears as an ellipse whose minor axis is foreshortened but whose major axis measures about the same as if the crater were centrally located. Surface curvature has little effect on this measurement because most craters are small ...

1

At least some of the 'active asteroids' recently observed are most likely the result of impacts. One example is 2010 A2: For more details, see https://en.wikipedia.org/wiki/P/2010_A2_(LINEAR).

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