Differences
See also: Lunar mareThe two hemispheres have distinctly different appearances, with the near side covered in multiple, large maria (Latin for 'seas,' since the earliest astronomers incorrectly thought that these plains were seas of lunar water). The far side has a battered, densely cratered appearance with few maria. Only 1% of the surface of the far side is covered by maria, compared to 31.2% on the near side. One commonly accepted explanation for this difference is related to a higher concentration of heat-producing elements on the near-side hemisphere, as has been demonstrated by geochemical maps obtained from the Lunar Prospector gamma-ray spectrometer. While other factors such as surface elevation and crustal thickness could also affect where basalts erupt, these do not explain why the farside South Pole-Aitken basin (which contains the lowest elevations of the Moon and possesses a thin crust) was not as volcanically active as Oceanus Procellarum on the near side.
Another factor in the large difference between the two hemispheres is that the near side has been shielded from impacts by the Earth via the synchronous rotation that keeps the far side exposed to impactors coming from outer space.
It has also been proposed that the differences between the two hemispheres may have been caused by a collision with a smaller companion moon that also originated from the Theia collision. In this model the impact led to an accretionary pile rather than a crater, contributing a hemispheric layer of extent and thickness that may be consistent with the dimensions of the farside highlands.
Read more about this topic: Far Side Of The Moon
Famous quotes containing the word differences:
“The mother must teach her son how to respect and follow the rules. She must teach him how to compete successfully with the other boys. And she must teach him how to find a woman to take care of him and finish the job she began of training him how to live in a family. But no matter how good a job a woman does in teaching a boy how to be a man, he knows that she is not the real thing, and so he tends to exaggerate the differences between men and women that she embodies.”
—Frank Pittman (20th century)
“I don’t know what immutable differences exist between men and women apart from differences in their genitals; perhaps there are some other unchangeable differences; probably there are a number of irrelevant differences. But it is clear that until social expectations for men and women are equal, until we provide equal respect for both men and women, our answers to this question will simply reflect our prejudices.”
—Naomi Weisstein (b. 1939)
“The extent to which a parent is able to see a child’s world through that child’s eyes depends very much on the parent’s ability to appreciate the differences between herself and her child and to respect those differences. Your own children need you to accept them for who they are, not who you would like them to be.”
—Lawrence Balter (20th century)