Chris Peterson wrote:
Guest wrote:FIFTY YEARS AGO TODAY, February 20, 1962, Astronaut John Glenn (age 40), on-board Project Mercury capsule Friendship 7, circled the Earth three times. A savvy test pilot, Glenn took manual control of the spacecraft during the first orbit and maintained control for the remainder of the flight, when the automatic stabilization and control system failed.
So why are we looking at Barred Spiral Galaxy NGC 1073?
Not much has ever really come directly from manned space flight. But there was a strong political will to make that happen (got to stay ahead of those Russkies, you know...), and the technology and skills developed flowed into unmanned space exploration, which has produced a vast increase in human knowledge of the Universe. Today's APOD is a much better piece to highlight the legacy of the early space program than yet another historical photo of Friendship 7, like just about every other publication on Earth is running today!
The lunar module Eagle landed at Mare Tranquillitatis on July 16, 1969. The site was chosen because it was relatively free of craters and boulders. The astronauts collected 22 kg of material including 50 rocks, soil samples, and 2 core tubes which contained material from a depth of 13 cm and less.
Two main kinds of rocks were collected, basalts and breccias. Samples showed no evidence of any water or any living organisms.
Basalts are volcanic and contain solidified molten lava. They are found on the Earth, also.
Breccias are made up of fragments of older rocks. The older rocks have already been fragmented by the bombardment of meteorites. The heat and pressure of the impacts can subsequently fuse these older fragments into newer rocks, and these newer rocks are called breccias.
Again in a relatively smooth area of few craters and boulders, the Apollo 12 made a precision landing on Oceanus Procellarum on November 19, 1969, only 600 meters from the Surveyor III spacecraft, which had landed on the Moon on November 19, 1969. The success of this precision landing cleared the way for future landings in more difficult terrain.
34 kg of samples were collected including 45 rocks, soil samples, and several core tubes. The majority of rocks were basalts, and only 2 breccias were returned. The basalts proved to be 3.1 to 3.3 billion years old. That was 500 million years younger than the basalts returned with Apollo 11, suggesting that volcanic activity on the Moon did not occur in a single event.
A rock which came to be known as KREEP was found near the landing site. It was rich in potassium (K), rare earth elements (REE) and phosphorus (P). More KREEP specimens were found on later missions. KREEP is believed to come from an early time in lunar evolution, during the solidification of the Moon’s molten stage.
Lunar landing was made at Fra Mauro highlands on January 31, 1971. This area was formed by material ejected by the impact that formed the Imbrium Basin. As expected, most of the 42 kg of rocks and soil collected were breccias. Many of the breccias were enriched with KREEP.
Some basalts were collected. They were usually clasts (i.e., fragments) in breccias. These basalts were 4.0 to 4.3 billion years old, the oldest volcanic activity in any mare location demonstrated during the Apollo program.
Lunar landing took place on July 30, 1971 on the edge Imbrium Basin where the Apennine Mountains form a rim of the Imbrium Basin. Nearby Hadley Rille, a channel in the mare, was thought to be formed by volcanic activity. A mass of 77 kg was collected, including 370 individual rock and soil samples.
The surface of Mare Imbrium was composed of basalt. Pyroclastic glass beads were also found at the landing site. These glass beads are formed by a process, which also occurs on Earth, where lava is explosively hurled high above the surface and then cools very quickly. The most common glass beads were green in color, due to large amounts of magnesium.
The Apennine Mountains were formed by the by the Imbrium basin impact, and it was hoped that samples collected there might contain ancient rocks. These rocks showed that the impact occurred 3.84 to 3.87 billion years ago.
The astronauts collected an anorthosite, a rock composed almost entirely of the mineral plagioclase, at Spur Crater on Mount Hadley Delta. This became known as the Genesis Rock. Early in the evolution of the Moon, the outer layers were molten. This stage is known as the magma ocean. Anorthosite, rich in plagioclase, floated on the surface as the magma ocean cooled. The Genesis Rock was dated to 4.0 billion years, but it may have undergone metamorphic alteration at that time and could be considerably older.
The lunar module Orion landed alongside the Descartes Mountains on April 21, 1972. 96 kg, including 731 rock and soil samples were returned.
Nearly every rock collected during the Apollo 16 mission was a breccia, indicating that this area was covered by impact debris and not volcanic planes. Two anorthosite specimens were found. One of these proved to be 4.44 to 4.51 billion years old, nearly the age of the Moon itself.
On December 11, 1972, the Apollo 17 lunar module landed in Taurus-Littrow, a deep, narrow valley in the Montes Taurus, mountains that form the rim of the Serenitatis basin. This was the only mission to actually have a geologist on board.
11 kg were returned, including 741 rock and soil samples. One sample was a deep drill specimen. Material as deep as 3 meters below the lunar surface was obtained. It was hoped that ancient rocks might be found in the highlands, while the floor of the valley might show evidence of young volcanic activity.
As expected, rocks from the floor of the Taurus-Littrow valley were mostly basalts. As with the Apollo 15 mission, volcanic glass was also found. The famous “orange soil” found at the rim of Shorty Crater, turned out to be a mixture of orange and black volcanic beads.
Several kinds of old rocks were collected in the mountains both to the north and the south of the landing site. Impact melts, melted by the heat of a very large impact event, were 3.89 billion years old. They formed during the creation of the Serenitatis basin. Norite, troctolite, and dunite, also found in the mountains, were found to be 4.2 to 4.5 billion years old.