Located at an altitude of 1740 metres, Mount Wilson Observatory got its start in 1904 when George Ellery Hale signed a free, 99-year lease for 40 acres at the summit to build world-class telescopes.
Then Hale erected the Snow Solar Telescope (1905), a 60-inch reflector (the world's largest when completed in 1908), the 150-foot Solar Tower, and finally the 100-inch Hooker Telescope (1918), which Edwin Hubble used to discover that the universe is expanding.
Despite being swamped with light pollution from the 13 million residents to its immediate south and southeast, the observatory has regained much of its scientific relevance.
In recent years, Mount Wilson has served as a test-bed for adaptive-optics and interferometric imaging. It's the main facility of Georgia State University's Center for High Angular Resolution Astronomy (CHARA) and the site of the University of California's Infrared Spatial Interferometer (ISI).
To explain deposits of minerals containing calcium, magnesium, and iron, in the rock, Niles and his colleagues suggest the rock was sitting at or near the surface of Mars, with water rich in carbon dioxide bubbling up to the surface in the area from deep underground, perhaps as part of a hot spring.
The relative amounts of the three metals deposited from solution depend on the temperature of the water they were dissolved in. The team used previous measurements of these amounts to calculate a water temperature of less than 100 °C. This was not a certainty beforehand, since water can remain liquid above that temperature at the higher pressures underground.
"These minerals were formed in what is very likely to have been a habitable environment," Niles says.REPAIR or replace? In these frugal times, you would think the answer would always be a resounding repair. But surprisingly, until the final mission to service the Hubble Space Telescope last May, any instrument that failed on board was simply replaced. When two essential imaging instruments stopped working in the period running up to the mission, however, the crew decided a more sustainable approach was needed.
This was no easy task. "We know how to replace instruments and electrical connectors but we had never attempted to go inside the guts of an instrument and fix it in space," says Michael Weiss, deputy programme manager for Hubble at NASA's Goddard Space Flight Center in Greenbelt, Maryland. Repairing such complex equipment is usually done on a sterile bench inside a laboratory cleaner than an operating theatre, with each step taken painstakingly precisely - not something easily done in a pressurised spacesuit.
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Then Hale erected the Snow Solar Telescope (1905), a 60-inch reflector (the world's largest when completed in 1908), the 150-foot Solar Tower, and finally the 100-inch Hooker Telescope (1918), which Edwin Hubble used to discover that the universe is expanding.
Despite being swamped with light pollution from the 13 million residents to its immediate south and southeast, the observatory has regained much of its scientific relevance.
In recent years, Mount Wilson has served as a test-bed for adaptive-optics and interferometric imaging. It's the main facility of Georgia State University's Center for High Angular Resolution Astronomy (CHARA) and the site of the University of California's Infrared Spatial Interferometer (ISI).
To explain deposits of minerals containing calcium, magnesium, and iron, in the rock, Niles and his colleagues suggest the rock was sitting at or near the surface of Mars, with water rich in carbon dioxide bubbling up to the surface in the area from deep underground, perhaps as part of a hot spring.
The relative amounts of the three metals deposited from solution depend on the temperature of the water they were dissolved in. The team used previous measurements of these amounts to calculate a water temperature of less than 100 °C. This was not a certainty beforehand, since water can remain liquid above that temperature at the higher pressures underground.
"These minerals were formed in what is very likely to have been a habitable environment," Niles says.REPAIR or replace? In these frugal times, you would think the answer would always be a resounding repair. But surprisingly, until the final mission to service the Hubble Space Telescope last May, any instrument that failed on board was simply replaced. When two essential imaging instruments stopped working in the period running up to the mission, however, the crew decided a more sustainable approach was needed.
This was no easy task. "We know how to replace instruments and electrical connectors but we had never attempted to go inside the guts of an instrument and fix it in space," says Michael Weiss, deputy programme manager for Hubble at NASA's Goddard Space Flight Center in Greenbelt, Maryland. Repairing such complex equipment is usually done on a sterile bench inside a laboratory cleaner than an operating theatre, with each step taken painstakingly precisely - not something easily done in a pressurised spacesuit.
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