在线英语听力室_免费在线英语听力学习网站

This is Scientific American’s 60-Second Science. I’m Karen Hopkin. This will just take a minute.

Many of the key molecules¹ for life have a specific direction, or handedness: DNA² twists to the right, amino acids to the left. Now scientists at the National Institute of Standards and Technology (or NIST) aim to take advantage of this so-called chirality to search for signs of extraterrestrial life.

When chemists synthesize organic compounds in the lab, they often wind up with a mix of molecules: half are right-handed, and half are left. But cells are a bit more particular. When life arose, our ancestors made some choices. They went with the right-handed sugars, and the left-handed amino acids, a tradition still in effect.

The scientists at NIST have come up with a gadget³ that can see the polarized light that bounces off of molecules that show a preferred handedness. And in the Proceedings⁴ of the National Academy of Sciences, they report using the device to detect the signature reflection that comes from the chlorophyll in plant leaves. If this handedness meter works well at a distance, they could load it onto a space probe—a preponderance of right- or left-handed biomolecules could mean a planet has at least simple life forms on it. And we might even find out if ET is a southpaw.

Thanks for the minute. For Scientific American’s 60-Second Science, I’m Karen Hopkin.