Wednesday, January 21, 2009
They found that a massive earthquake, or series of quakes, struck the seismically active region, collapsing walls and floors and launching landslides from barren mountain ranges surrounding the valley.
In addition, layers of silt indicate massive flooding followed.
Then came El Nino, a periodic change in the winds and currents in the Pacific Ocean, which brought heavy rains that damaged irrigation systems and washed debris into the streams and down to the ocean, where the sand and silt settled into a large ridge, sealing off the previously rich coastal bays.
Thursday, January 15, 2009
When the presence of methane was reported in 2004 by three teams of scientists, the findings generated surprise and skepticism because only a few explanations seemed to be plausible.
One was geothermal chemical reactions involving water and heat in volcanoes or underground hot springs. But evidence for recent volcanism on Mars is scarce. Also, volcanoes would be expected to spew other gases like sulfur dioxide, and those are not plentiful in the planet’s atmosphere.
A second possibility is biological. On Earth, a class of bacteria known as methanogens breathes out methane as a waste product.