In Kent's aorta model most of the tears are transverse, or across the artery, in a section called the isthmus, and they start on the intima, or the inner layer of the aorta.

FORBES: Smart Dummies

In a section on water in outer space we learn that there is a lake-size layer of ice on the moon's south pole, that Mars once had rivers, that there is steam in the sun's atmosphere.

FORBES: The Story Of Eau

Nitrous oxide is also considered a greenhouse gas and is 310 times more dangerous to the Earth's ozone layer than carbon dioxide, said Joseph Johns, chief of the U.S. attorney's environmental crimes section.

NPR: Feds Raid 17 Calif. Businesses For Nitrous Oxide