Whatever the reason you're on Mars, I'm glad you're there, and I wish I was with you.

Absolute certainty will always elude us. We will always be mired in error. The most each generation can hope for is to reduce the error. . . .

The prediction I can make with the highest confidence is that the most amazing discoveries will be the ones we are not today wise enough to foresee.

A stars rich in europium; of distant galaxies analyzed through the collective light of a hundred billion constituent stars. Astronomical spectroscopy is an almost magical technique. It amazes me still. Auguste Comte picked a particularly unfortunate example.

My view is that if there is no evidence for it, then forget about it. An agnostic is somebody who doesn’t believe in something until there is evidence for it, so I’m agnostic.

Science is not perfect. It's often misused; it's only a tool, but it's the best tool we have. Self-correcting , ever changing, applicable to everything: with this tool, we vanquish the impossible.

Even today the most jaded city dweller can be unexpectedly moved upon encountering a clear night sky studded with thousands of twinkling stars. When it happens to me after all these years it still takes my breath away.