Science & Technology

Two astronauts went on a last-minute spacewalk Saturday to replace a pump suspected of being the source of a serious ammonia leak.

It was unclear what caused the ammonia leak, NASA spokesman Rob Navias said, "but the installation of this spare pump package — at least at the moment — seems to have done the trick."

NASA officials called the spacewalk a success, but said it would take time to see if the leak was indeed stopped. Engineers will review photos the astronauts took at the site.

Climate scientists have a good reason to want to get away from it all. To get an accurate picture of the amount of carbon dioxide in the Earth's atmosphere, you have to find places where the numbers won't be distorted by cities or factories or even lots of vegetation that can have a major local impact on CO₂ concentrations.

Children with autism see simple movements twice as fast as other children their age, a new study finds.

Researchers at Vanderbilt University and the University of Rochester were looking to test a common theory about autism which holds that overwhelming sensory stimulation inhibits other brain functions. The researchers figured they could check that by studying how kids with autism process moving images.

Earth's atmosphere is entering a new era. A mountaintop research station that has been tracking carbon dioxide for more than 50 years says the level of that gas in our air has reached a milestone: 400 parts per million.

That number is one of the clearest measures of how human beings are changing the planet. It shows how much carbon we have put into the air from burning fossil fuels — and that carbon dioxide drives global warming.

This measurement comes from Mauna Loa, Hawaii, a remote volcano where the air is largely free of local influences.