Scanning the Heavens

The recent exercise in December 2008 by the US Air Force to assess the ability to cope with a collision with a Near Earth Object again highlighted how limited is the Earth's capability to detect or prevent such an event taking place. Recently however a Near Earth Object did indeed come into contact with the Earth in October 2008. Designated 2008 TC3 this car sized object exploded over the Sudan but was only spotted by a telescope (the Catalina Sky Survey) with 20 hours notice and at a distance of 500,000 kilometres from our planet. Although the likelihood of a catastrophic asteroid collision is extremely rare, the potential for a strike from a smaller but still destructive near earth body has much greater plausibility.

This situation again raises the need for a greater overall surveillance of the space around Earth and in relation to the Earth's orbit around the Sun. The proposal to increase surveillance through the Panoramic Survey telescope and Rapid Response System (Pan-STARRS) as well as the proposed Large Synoptic Survey Telescope in Chile (providing the project is completed by 2015) will complement the existing monitoring programs. The next question is what action to take if a large body is located on a trajectory to Earth.

Geothermal energy - a price too high to pay?

From the New York Times, 10 September 2009

The question of harnessing the earth's own capacity for energy generation should be measured against possible other effects and risks as the article below outlines.

LANDAU IN DER PFALZ, Germany — Government officials here are reviewing the safety of a geothermal energy project that scientists say set off an earthquake in mid-August, shaking buildings and frightening many residents of this small city. The geothermal plant, built by Geox, a German energy company, extracts heat by drilling deep into the earth. Advocates of the method say that it could greatly reduce the world’s dependence on fossil fuels by providing a vast supply of renewable energy.


But in recent months, two similar projects have stirred concerns about their safety and their propensity to cause earthquakes. In the United States, the Energy Department is scrutinizing a project in Northern California run by AltaRock Energy to determine if it is safe. (The project was shut down by the company last month because of crippling technical problems.) Another project, in Basel, Switzerland was shut down after it generated earthquakes in 2006 and 2007 and is awaiting the decision of a panel of experts about whether it can resume.

The Landau project will be allowed to continue operating while the review panel, which held its first meeting last Friday, deliberates. Geox officials initially denied any responsibility for the temblor and continue to dispute the government’s data linking the project to the quake. The panel will, among other things, have to sort through the conflicting data presented by the company and government scientists.

Like other earthquakes that have been attributed to geothermal plants, the Landau temblor was sudden and brief and was accompanied by a sound that in some cases has been likened to a sonic boom. There were no injuries and there was no known structural damage to buildings in the city. But the 2.7 magnitude quake has stoked fears and set off debate in the state Parliament, which subsidized the construction of the plant, about the method’s safety.

In interviews last week, Geox officials conceded that the plant had set off tiny earthquakes and said that they were not certain what set off the Aug. 15 temblor. But consultants for the company dispute the data cited by government scientists to back up their conclusion that the project caused the earthquake: their own data, they said, proves that the quake originated more than two miles from the site of the plant and six miles below the earth’s surface. Those figures would essentially rule out a connection with the plant.

The Landau plant, which cost $30 million, went into operation in 2007 and produces electricity for 6,000 homes by drawing heat from beneath the bedrock, nearly two miles beneath the earth’s surface. Geox said a coal-burning plant producing the same electricity would emit 30,000 tons of carbon dioxide annually.
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