Atom & Cosmos

How the moon got its water, plus more in this week’s news

Titan’s cirrus clouds
The Cassini spacecraft has measured the abundance and composition of wispy clouds high in the smoggy atmosphere of Saturn’s frigid moon Titan. The cirruslike ice clouds, which Cassini finds throughout the atmosphere, can be used to trace the changing abundance of icy particles — nitrites and hydrocarbons — at different altitudes and with Titan’s seasons, Carrie Anderson of NASA’s Goddard Space Flight Center in Greenbelt, Md.,