Measuring Mercury’s Craters

Images of craters obtained by MDIS from orbit. Left: A simple, bowl-shaped crater 4.1 km in diameter crater located at 78.8?N, 346.3?E. Solar illumination is from the south. Right: A complex crater 51.5 km in diameter located at 2.3?N, 121.4?E. Illumination is from the east. Shadows cast on a crater interior can be used to estimate the depth of a crater floor below the surrounding rim.

Getting to know a planet well is getting to know its surface features. Through measuring impact craters, planetary scientists are able to disclose information such as the origin and evolution of Mercury’s surface. We know it’s a matter of numbers, but just exactly how is it done when you can’t physically be there?

Size, shape and structure of craters is the common bond that most solar system bodies share. By understanding the physics of how they were made, researchers are able to draw conclusions through modeling. Their laboratory impact experiments and numerical simulations make judging crater qualities doable on a planetary scale. To further refine their results, it is then compared against known data for new, as well as eroded, craters. This information then gives us a clearer idea of surface properties, such as mineral deposits, soil composition, ice deposits, proportions and more. Checking out shapes and sizes on Mercury with observations obtained by the MESSENGER spacecraft are just the beginning.

Why is a Mercury crater investigation so important? Maybe because its surface gravitational acceleration (3.7 m/s2) is nearly identical to that at Mars. In this case, gravity plays an important role as the “transition diameter” is affected. According to the study, “Simple craters tend to be bowl shaped, whereas complex craters have terraced walls and can contain a central peak. If gravity were the dominant factor controlling the transition diameter, one would expect that this diameter would be similar on Mercury and Mars.” These transition diameters observed on Mercury are important because they give us clues to the Martian crust. Their differences could mean a weaker surface due to near-surface water ice.

An example complex crater on Mercury, ~ 55 km in diameter and centered near 63.5°N, -139?E, that has been imaged by MDIS (left) and profiled by MLA (right). A slightly larger complex crater lies along the MLA profile to the south.

The Mercury Laser Altimeter (MLA) and the Mercury Dual Imaging System (MDIS) are hard at work providing the photo data needed to study cratering. We’re now able to get an inside look at central peaks, walls, floors and slopes. In addition, we’re getting a concise measurement of diameters. As with the Moon, researchers can make assessments as to depth by measuring the shadows. While MLA cannot always be used for these types of measurements, these fresh insights are furthering our understanding of crater properties – both on Mercury and across all holey bodies in our solar system.

Original News Source: Messenger News.

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Spectacular View from LRO of Tycho Crater’s Central Uplifts

Oblique view of Tycho crater. Credit: NASA/GSFC/Arizona State University.

Here’s the Moon like you’ve never seen it before: a dramatic sunrise view of Tycho Crater on the Moon, highlighting the peaks and crags of the crater’s central uplifts. On June 10,2011 the Lunar Reconnaissance Orbiter slewed 65° to the west, allowing the Narrow Angle Camera to capture a “sideways” look at Tycho crater, resulting in a spectacular image. The central peak complex is about 15 km wide southeast to northwest (left to right in this view). Below are more images and a video which spans and zooms in to the entire image.

Tycho Crater is a very popular target with amateur astronomers since it is easily seen from Earth. The crater measures about 82 km (51 miles) in diameter, and the summit of the central peak is 2 km (6562 ft) above the crater floor, and the crater floor is about 4700 m (15,420 ft) below the rim.

Central uplifts form in larger impact craters in response to the impact event.

LROC principal investigator Mark Robinson wrote on the LRO website, “Tycho’s features are so steep and sharp because the crater is young by lunar standards, only about 110 million years old….Were these distinctive outcrops formed as a result of crushing and deformation of the target rock as the peak grew? Or do they represent preexisting rock layers that were brought intact to the surface? Imagine future geologists carefully making their way across these steep slopes, sampling a diversity of rocks brought up from depth.”

Here’s a close-up of the summit. The boulder in the background is 120 meters wide, and the image is about 1200 meters wide.

Oblique view of summit area of Tycho crater central peak. Credit: NASA/GSFC/Arizona State University

And here’s the entire crater:

LROC WAC mosaic of Tycho crater with lighting similar to that when the NAC oblique image was taken. Mosaic is 130 km wide, north is up. Credit: NASA/GSFC/Arizona State University.

Click on the images for larger versions on the LROC website, or see this link for more information on these images.

Source: LROC

Tagged as: Lunar Reconnaissance Orbiter, Moon, Tycho Crater

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