Tag: impact craters

Triple impact on Moon

11:27 am

Impact craters Messier and Messier A on the Moon

Cool image time! A new image release from Lunar Reconnaissance Orbiter (LRO) takes a look at the impact process that created the crater Messier and its neighbor crater Messier A. The photo to the right, cropped to post here, shows both craters.

Take a close look at Messier A. It is actually a double crater itself. From the release:

Messier A crater, located in Mare Fecunditatis, presents an interesting puzzle. The main crater is beautifully preserved, with a solidified pond of impact melt resting in its floor. But there is another impact crater beneath and just to the west of Messier A. This more subdued and degraded impact crater clearly formed first.

Did these three craters happen as separate events. According to the data, it appears no. Instead, they might have all been part of a single rain of asteroids, all occurring in seconds.
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Martian impacts and streaks

12:18 pm

Slope-streaked crater on Mars
Click for full image.

In the most recent image download from the high resolution camera on Mars Reconnaissance Orbiter (MRO), there was the cool image to the right, reduced and cropped to post here, of a crater that appeared to have hundreds and hundreds of slope streaks along its inner slopes.

Slope streaks are quite mysterious. They are found in the equatorial regions as dark (though sometimes light) streaks on steep slopes, appearing throughout the year and slowly fading over time. They also appear to be a geological phenomenon unique to Mars. Nothing on Earth or any other planet appears to correspond.

As such, their nature and cause remains unknown, though there are a bunch of theories, with the most popular being that these are a kind of dust avalanche. They are always found in connection with dust-covered terrain, but they also make no significant topological change to the surface, other than brightness.

The slope streaks in this crater are especially intriguing, because of the number of streaks. In digging further into the MRO archive I found a number of images of this crater and its surrounding terrain. It appears that sometime before 2012 there was a relatively recent impact close to the exterior of the eastern rim of this crater. The image below, taken in 2014 by MRO, shows this impact as the large dark splotch, with the new crater indicated by the arrow..
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New impact craters on Mars

1:49 pm

New impact crater on Mars

Cool image time! The high resolution camera on Mars Reconnaissance Orbiter (MRO) keeps finding recent impact craters, all of which the science team try to monitor periodically to see how the surface evolves over time. The image on the right, cropped to post here, is one such crater, the image taken in January 2018 and released with as one of the captioned images from this month’s image catalog release. If you click on the image you can see the full picture.

What is notable about this particular impact are the colors.

The new crater and its ejecta have distinctive color patterns. Once the colors have faded in a few decades, this new crater will still be distinctive compared to the secondaries by having a deeper cavity compared to its diameter.

Those colors of course have importance to researchers, as they reveal the different materials found beneath the surface at this location, normally hidden by surface dust and debris.

Nor is this the only impact crater revealed in this month’s image release. Earlier in the month the science team highlighted an image that captured two small impacts. While all three of these impacts are in the general region called Elysium Planitia, they are not particularly close to each other. They are however surrounding the landing site for the InSight lander now heading to Mars. This last link takes you to my January 28, 2018 post detailing some information about this landing site, and also includes another recent crater impact, found at the center of the landing zone.

It is not clear if these recent impacts are related to each other. As noted by Alfred McEwen of the science team, “Often, a bolide breaks apart in the atmosphere and makes a tight cluster of new craters.” It could be that all these recent impacts came from the same bolide, which is why there appear to be a surplus of them in Elysium Planitia.

Then again, our surface survey of Mars is very incomplete. These impacts could simply be marking the normal impact rate for Mars. We will not know until we have completed a detail survey of all recent impacts on Mars, and have been able to date them all.

Who wants to do it?

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200 new lunar impact craters discovered

9:18 am

In a paper [pdf] presented this week at a lunar science conference, scientists announced the identification of more than 200 new impact craters on the Moon from Lunar Reconnaissance Orbiter (LRO).

As of 1 May 2015, we have scanned and classified changes in 14,182 NAC temporal pairs using our automated change detection tool leading to the discovery over 200 impact craters ranging in size from 1.5 to 43 m. In addition, we also identified thousands of other surface changes, including about 44,000 low reflectance splotches, 3,500 high reflectance splotches, 850 mixed reflectance splotches, [and] 1 Chinese lander/rover.

They think the splotches are created from impacts too small to see with LRO.

Hat tip James Fincannon.

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