Mars is the fourth planet from the Sun in our solar system. It is named after the Roman god of war Mars (Ares in Greek mythology) because of its apparent red color. This feature has also earned it the nickname "The Red Planet". The prefix areo- refers to Mars in the same way geo- refers to Earth. The astronomical symbol for Mars is ♂, a circle with an arrow pointing northeast. The Chinese, Korean, Japanese, and Vietnamese cultures refer to the planet as 火星, or fire star. Mars is a terrestrial planet with a thin atmosphere, having surface features such as craters, giant valleys, and volcanoes. Of all the planets in our Solar System other than Earth, Mars is the most likely to harbor liquid water, and perhaps life.
As part of the wider Mariner program, in 1969Mariner 6 and Mariner 7 (Mariner Mars 69A / 69B) completed the first dual mission to Mars, flying over the equator and south polar regions and analysing atmosphere and surface with remote sensors as well as recording and relaying hundreds of pictures. The mission's goals were to study the surface and atmosphere of Mars during close flybys to establish the basis for future investigations, particularly those relevant to the search for extraterrestrial life, and to demonstrate and develop technologies required for future Mars missions and other long-duration missions far from the Sun. Mariner 6 also had the objective of providing experience and data which would be useful in programming the Mariner 7 encounter 5 days later.
Percival Lawrence Lowell (March 13, 1855 – November 12, 1916) was a businessman, author, mathematician, and astronomer who fueled speculation that there were canals on Mars, founded the Lowell Observatory in Flagstaff, Arizona, and formed the beginning of the effort that led to the discovery of Pluto 14 years after his death. The choice of the name Pluto and its symbol were partly influenced by his initials PL.
The hole was discovered by chance on images of the dusty slopes of Mars' Pavonis Mons volcano taken by the HiRISE instrument aboard the robotic Mars Reconnaissance Orbiter currently circling Mars. The hole appears to be an opening to an underground cavern, partly illuminated on the image right. Analysis of this and follow-up images revealed the opening to be about 35 meters across, while the interior shadow angle indicates that the underlying cavern is roughly 20 meters deep. .
