exploration

In 2005, we came the closest we ever had before to drilling into the mantle: the layer beneath the Earth's crust. Now, with new drilling technology adapted from the oil and gas industry, scientists might finally be ready to reach that holy grail of depth.

About halfway through our cover story on the next generation of manned submarines, you'll find a provocative dispute between two legendary figures over the respective merits of manned and unmanned exploration of the ocean.

In July, the space shuttle Discovery is slated to deliver two tons of hardware and supplies to the partially built International Space Station. This mission is paid for. As for the 16 more needed to finish assembly, as mandated by President George W. Bush two years ago in his Vision for Space Exploration policy, NASA is short by as much as $5 billion.