A possible small lateral lava flow is visible near the end of the feature. The crater lies in the gently sloping Snake River Plain, a broad expanse of volcanic rock with craters and linear and sinuous features thought to have formed in the same manner as their lunar counterparts.
Apollo astronauts studied this area in preparation for lunar missions. The crater pictured is approximately m in diameter, and the associated channel is over 5 km long. The resemblance to lunar "cobra head" rilles like the one in fig. The rilles are at least partly controlled by fracture and most originate in craters. Rille A, beginning on the flank of the crater Prinz, appears to have had a distinct two cycle history, producing crater in crater and rille in rille structures.
Rille B crosses a ridge of highland material without deviation or deformation, suggesting that the feature was superposed-that is, let down-from an earlier higher mare surface; the ridge appears to have been eroded. A shallow narrow rille not visible in this photograph occurs within the broader valley of rille C and is traceable across the elongate collapsed depression that bisects the main rille.
Craters at the heads of rilles probably represent source vents for fluids that either eroded the rilles or formed lava tubes that drained, contributing to the volume of mare lava in Oceanus Procellarum.
Ejecta from the young crater Aristarchus forms lightcolored streaks or "rays" across the dark mare surface; the high albedo of the rays may be due in large part to disruption of the surface by secondary craters. Rima Prinz I 1 graphically displays many of the features considered to be indicative of lunar basaltic lava channels.
The rille starts in a crater on the side of the ancient crater Prinz just off the photograph and descends about m, becoming narrower and shallower downslope. It is a "two story" channel with a broader older channel and crater inside of which is a younger, more sinuous, channel with its source vent. Samples returned by Apollo 15 from the very similar looking Rima Hadley were from a vesicular full of holes formed by gas bubbles flow of layered basalt.
The next channel to the west 2 also gets narrower and shallower downslope. It is the best example of distributaries-that is, a branching network of smaller channels at the downstream end of a larger channel. Krieger 3 is a "Gambart type" crater inferred to be volcanic in origin. Its flat floor, irregular shape, and highly irregular external deposits resemble the crater Gambart south of Copernicus, which was studied in by Apollo 17 astronaut H.
The deposits from Krieger lie on the surface of the mare basalts, indicating that the crater is quite young.
Its youthfulness is confirmed by the freshness of the crater floor deposits and the characteristic shape of these deposits. A nice example of a sinuous rille, interpreted as a lava channel 4 , runs out of the crater onto the mare surface. This lava surface is marked by wrinkle ridges 5 - complex mare ridges, generally asymmetric, with a braided ridge along one edge.
These ridges are interpreted to be faults or breaks in the mare lava flows along which a later generation of molten lava has been both intruded, raising the already cooled mare lava flows, and extruded onto the mare surface. Under certain lightning conditions it appears that there is a disturbance running at right angles that crosses the middle section of the valley. At km long and 12km across at its widest point, this is a major feature on the lunar landscape that is easy to see even with small instruments.
For dedicated lunar observers, spotting or imaging this little rille is seen as a significant achievement. Rima Hadley is best known because Apollo 15 landed just to the north of it, giving us exciting close-up views of the feature taken from the lunar surface.
You can resolve the rille in an 8-inch scope, though its narrow width of just 2km means that the seeing needs to be stable. Rima Hadley takes its name from the nearby Apennine mountain known as Mons Hadley, which is 4,m high.
The rille resembles a sinuous, meandering river as it crosses a flat, lava-filled region within the Apennine Mountains: an extension of the unpleasant sounding Palus Putredinus, the Marsh of Decay.
You can locate this region by drawing the shortest line possible between the southeastern rim of 85km-wide crater Archimedes and the mountains.
The rille continues on to a mountainous outcrop, passing around its base before coming to an end. The cracks are fine and intersect in many places, forming a network that stretches right across Gassendi. High-resolution shots from spacecraft show that the rim is actually intact, and that the lava that flowed into crater probably entered it beneath the rim. The famous Giant's Causeway in Northern Ireland is a classic example on the small scale, but even in bigger settings, such as in East Africa's rift valleys, geological lines tend to intersect in this way.
Procellarum's giant rectangle does the same, too - because the entire feature is draped over a sphere. This means the angles at the corners are wider than 90 degrees. For structures on this scale, a polygon with degree angles at the corners actually has four sides instead of six," explained Prof Andrews-Hanna.
The team cannot tell when the rifting occurred, but the dating of Moon rocks brought back by Apollo would suggest the valleys were filled by volcanic lavas about 3. The new study goes some way to resolving arguments over the origins of Procellarum, which looks different to other, more circular mare dark regions on the Moon's surface. For these regions, big asteroid impacts were more important in sculpting their forms.
The study is also further proof of the value of the Grail mission, led from the Massachusetts Institute of Technology. This comprised two, near-identical satellites that chased each other around the Moon over the course of a year.
They mapped changes in the pull of gravity as they flew over areas of differing mass. Far over to the east are the Taurus Mountains Montes Taurus , the landing place of the last of the manned lunar explorers, Apollo Two major mountain ranges divide two other features of the lunar landscape. Where these two meet is the prominent mountain Mons Hadley, named for British optician and instrument maker John Hadley — Apollo 15 landed here in July The lunar Alps, the Montes Alpes, sweep off to the northwest, enclosing the perfect oval crater, Plato.
On the barren floor of the Mare Imbrium are two of the most impressive single mountain peaks on the surface of the moon, Mons Piton and Mons Pico. The Mons Piton has a base 16 miles 25 kilometers in diameter and towers 7, feet 2, m over the surrounding plain.
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