Moon and Earth from Chang'e 5-T1

 Described at times as a big blue marble, from some vantage points Earth looks more like a small blue marble. Such was the case in this iconic image of the Earth and Moon system taken by the Chang'e 5-T1 mission last week. The Moon appears larger than the Earth because it was much closer to the spacecraft's camera. Displaying much of a surface usually hidden from Earth, the Moon appears dark and gray when compared to the more reflective and colorful planet that it orbits. The robotic Chang'e 5-T1 spacecraft, predominantly on an engineering test mission, rounded the Moon last Tuesday returned to Earth on Friday.

A break in the clouds

A break in the clouds on October 29, 2014, allowed scientists the opportunity to fly over Pine Island Glacier—one of Antarctica’s most rapidly changing areas. The flight was part of NASA’s Operation IceBridge, a mission that makes annual surveys of Greenland and Antarctica with instrumented research aircraft.

After months of darkness in Antarctica, the Sun continues to rise a little higher each day. IceBridge project scientist Michael Studinger captured this photograph of late day sunlight striking glaciers and mountains in coastal West Antarctica at the end of the October 29 survey of Pine Island Glacier.

The recent, rapid changes at Pine Island have made it a high priority target for IceBridge. The weather, however, is not always agreeable. Paths flown in 2014 were last surveyed by IceBridge in 2012, and prior to that from 2002 to 2009. In 2013, satellite imagery found that a large iceberg had separated from the glacier's calving front. During the first 2014 flight, instruments found a new crack—a relatively common feature, according to scientists.

Repeat measurements of land and sea ice from aircraft extend the record of observations once made by NASA's Ice, Cloud, and Land Elevation Satellite, or ICESat, which stopped functioning in 2009. In addition to extending the

Thin sections of Limburgite

Shown above are thin sections of Limburgite, an augite composed of olivine and glass-bearing, tephritic volcanic rock. The top view is shown under plane polarized light and the bottom view under crossed polarized light. The study of microscopic features using a polarizing or petrographic microscope is called thin section petrography. Thin sections allow for more accurate characterization of minerals in rock samples.

These specimens, several millimeters across, date from the Miocene and were found in the Kaiserstuhl Hills of southwestern Germany. Both views portray what is called hourglass zoning. The occurrence of this mafic rock in close proximity to the Rhine River made it convenient to quarry during the 19th century.

Largest landslide

Largest landslide

Saidmarreh landslide is located in western Iran.

Landsat image of Saidmarreh Landslide in Saidmarreh, Iran. The source area of the slide is bounded on the southwest by the crest of the Kabir Kuh anticline. Debris from the slide travelled down the flank of the anticline, across the Karkheh River and continued across the valley floor. Some material in the slide was carried a distance of 14 kilometers (9 miles).

One of the largest landslides that can be easily recognized on satellite images is the Saidmarreh Landslide in western Iran. The slide occurred about 10,000 years ago when about 20 cubic kilometers (about 5 cubic miles) of Lower Miocene and Eocene limestone detached along bedding planes and slipped down the north flank of the Kabir Kuh anticline. The maximum vertical descent was about 1600 meters (5250 feet).

The sliding slab was about 15 kilometers (9 miles) wide and had a surface area of about 165 kilometers (64 square miles). Debris from the slide crossed the Karkheh River at the base of the slope and spread across the valley floor. Some material in the slide had a travel distance of over 14 kilometers (9 miles).

The slide debris dammed the Karkheh River, causing a large lake to form behind the dam. The lake persisted long enough for up to 150 meters of sediment to accumulate on its bottom (these sediments currently support several thousand acres of cultivated land). The lake then breached the dam and eroded a channel through it. The current landscape is shown in the Landsat image at the top of this page and in the Google satellite image in the right column.  

How did those big rocks end up on that strange terrain?

 How did those big rocks end up on that strange terrain? One of the more unusual places here on Earth occurs inside Death Valley, California, USA. There a dried lakebed named Racetrack Playa exists that is almost perfectly flat, with the odd exception of some very large stones, one of which is pictured above. Now the flatness and texture of large playa like Racetrack are fascinating but not scientifically puzzling -- they are caused by mud flowing, drying, and cracking after a heavy rain. Only recently, however, has a viable scientific hypothesis been given to explain how 300-kilogram stones ended up near the middle of such a large flat surface. Unfortunately, as frequently happens in science, a seemingly surreal problem ends up having a relatively mundane solution. It turns out that high winds after a rain can push even heavy rocks across a momentarily slick lakebed.

Zagros Mountains

In southern Iran, the collision between the Asian landmass and the Arabian platform has folded rocks and pushed up the rugged Zagros Mountains. In places, underlying deposits of salt have ascended in fluid-like plumes. Some of these plumes have pushed through the rock above, like toothpaste from a tube, and they are now visible as darkish irregular patches. This image shows a few of over 200 similar features—called diapirs, or salt plugs—that are scattered about this part of the Zagros Mountains.

Gravity has caused the salt to flow like glaciers into adjacent valleys. The resulting tongue-shaped bodies are more than 5 kilometers long, with repeating bow-shaped ridges separated by crevasse-like gullies and with steep sides and fronts. The darker tones are due to clays brought up with the salt, as well as the probable accumulation of airborne dust. This ASTER perspective view was created by draping a band 3-2-1 (RGB) image over an ASTER-derived Digital Elevation Model (2x vertical exaggeration), and was acquired on August 10, 2001.

The Zagros Mountains in southwestern Iran

The Zagros Mountains in southwestern Iran present an impressive landscape of long linear ridges and valleys. Formed by collision of the Eurasian and Arabian tectonic plates, the ridges and valleys extend hundreds of kilometers. Stresses induced in the Earth’s crust by the collision caused extensive folding of the preexisting layered sedimentary rocks. Subsequent erosion removed softer rocks, such as mudstone (rock formed by consolidated mud) and siltstone (a slightly coarser-grained mudstone) while leaving harder rocks, such as limestone (calcium-rich rock consisting of the remains of marine organisms) and dolomite (rocks similar to limestone containing calcium and magnesium). This differential erosion formed the linear ridges of the Zagros Mountains. The depositional environment and tectonic history of the rocks were conducive to the formation and trapping of petroleum, and the Zagros region is an important part of Persian Gulf production.

This astronaut photograph of the southwestern edge of the Zagros mountain belt includes another common feature of the region—a salt dome (Kuh-e-Namak or “mountain of salt” in Farsi). Thick layers of minerals such as halite (common table salt) typically accumulate in closed basins during alternating wet and dry climatic conditions. Over geologic time, these layers of salt are buried under younger layers of rock. The pressure from overlying rock layers causes the lower-density salt to flow upwards, bending the overlying rock layers and creating a dome-like structure. Erosion has spectacularly revealed the uplifted tan and brown rock layers surrounding the white Kuh-e-Namak to the northwest and southeast (center of image). Radial drainage patterns indicate another salt dome is located to the southwest (image left center). If the rising plug of salt (called a salt diapir) breaches the surface, it can become a flowing salt glacier. Salt domes are an important target for oil exploration, as the impermeable salt frequently traps petroleum beneath other rock  layers