How do lunar rays form

The Role of Cosmochemistry C hemical analyses of lunar samples provide "ground truth" to understand the geologic processes on the Moon. Specifically, the discoveries by cosmochemists of nanophase-iron grain coatings, Fe-Si phases, and other space weathering products in lunar rocks and meteorites have enabled us to better understand the physical, chemical, and optical changes that occur over time as the lunar surface is exposed to the space environment and matures.

Older surfaces in which these changes have reached a steady state are said to be fully mature. Younger surfaces are called immature. Space weathering products in the lunar material, which can only be discovered by sample analysis, affect the spectral signatures of the Moon's surface. Using scanning electron microscopy, they've measured, for example, the abundance of agglutinate glass and major minerals in grain-size separates of lunar regolith see photographs below.

This is a photograph in reflected light of a polished thin section of regolith from the Apollo 17 drill core. The big particle with round bubbles in it, in the center of the photograph, is an agglutinate impact glass bonded with rock, mineral, and glass fragments. Many small agglutinates are also visible. The abundance of these glassy particles increases with the amount of space weathering, or maturity. And average grain size decreases as the regolith matures. Larry Taylor and his colleagues used a scanning electron microscope like the one pictured above to analyze lunar soils in exquisite detail.

Putting It Together With Remote Sensing Data T hree types of data were compiled and analyzed by the research team to study the lunar rays. Near-IR reflectance spectra between 0. They used the shape and position of this band to determine the composition and relative abundance of pyroxene and olivine minerals, which helped them distinguish rock types.

Radar data at three wavelengths: 3. Surface and subsurface scattering properties of the Moon were analyzed using these radar backscatter images. The 3. The 70 cm data show roughness on scales from 50 cm to 10 m within 5 to 10 meters depth. Add a thin third layer by sprinkling cocoa over the top with a spoon. You can also use a sifter for a more even coating. The cocoa represents the surface layer on the Moon. Find a spot where you can safely and easily drop a rock into your cake pan.

You may want to put down a newspaper or a towel to catch any baking ingredients that come out of the pan. Simulate a rock impacting the Moon by holding a small rock above your head and dropping it into the cake pan.

Observe the "ejecta pattern" created by the impact. Did any of the sprinkles get ejected out of the crater? Gently remove the impactor.

Try dropping different size rocks from different angles and heights. How does the ejecta pattern differ from one impact to the next? Groups Why Join? Astronomy Day. The Complete Star Atlas.

This spectacular impact crater on Mars, imaged by HiRISE on the Mars Reconnaissance Orbiter, spans feet 30 meters and shows a clear system of rays in enhanced color.

Fiery chunks of rock are constantly bombarding the planetary bodies of our solar system, leaving behind long-lasting scars. These gouges, in the form of craters, can be used to learn about the history of our little nook in the vast universe, prompting scientists to study their features feverishly. Yet one pattern commonly found around craters has remained a puzzle.

Sometimes, these craters contain radial rays of debris fanned out around the impact zone. In the lab, scientists have tried to reproduce these patterns by dropping balls into containers of sand or beads, yet have found little success.

But in a recent study published June 27 in the journal Physical Review Letters , a team of scientists has finally made some progress in understanding how crater rays form, and their inspiration comes from an unexpected source: high school students. Tapan Sabuwala of the Okinawa Institute of Science and Technology Graduate University was scouring the internet for videos by other researchers, hoping to find someone who was producing crater rays in sandbox experiments.

Although none of the experts were achieving such a pattern, Sabuwala chanced across a video where high school students were producing the elegant rays. Our Moon shows several large craters with extended rays; notably Tycho Crater in the southern lunar highlands. Instead, they were starting with an uneven surface — one that more accurately reflects the natural landscapes of planets and moons. After realizing this, Sabuwala and his team got to work, conducting more experiments but this time starting with an uneven surface.

Using this approach, they finally gained critical insights into how crater rays are produced. The number of these rays depends on the ratio of the size of the ball to the size of the surface undulations; in terms of meteorite impacts, this is the equivalent of the size of the meteorite compared to the space between valleys on the surface of the affected moon or planet.

The straightforwardness of the model is surprising, says Sabuwala. This gives us a new and easy way to estimate the size of the impactor that formed a rayed crater. Their results suggest that crater rays are formed due to the interaction of a shockwave that is generated when the ball representing a meteorite strikes the surface.

If the surface is initially smooth, this creates a similarly smooth shockwave that disperses the ejected grains evenly — no rays. But with an uneven surface, this shockwave becomes asymmetrical, causing the ejecta to clump in some areas and form rays that splay out from the impact zone.

In particular, the rays form where the ball intersects with the edge of a dip in the surface in the case of planets or moons, the edge of a valley.