If only 30% of the forms come back, the bureau will sample six out of seven of the remainder.

ECONOMIST: Statistics

You rub the inside of each cheek for one minute to get a good DNA sample, put the swabs into the plastic tube provided, sign a few forms and send it all back.

FORBES: Magazine Article

The sample had between 20% to 30% of a type of clay called smectite, which forms in the presence of water, Blake said.

CNN: NASA: Yes, Mars could have hosted life