The two miniature probes carrying ten experimental technologies each failed to respond to a final communication effort by NASA engineers. The probes, which piggybacked aboard the Mars Polar Lander, were to slam into Martian soil December 3, 1999. Project manager Sarah Gavit said she couldn't envision any scenario in which the probes' batteries would still hold a charge after so many days on the planet.

Deep Space 2 is part of NASA's New Millennium Program, which develops cutting-edge technology and flight tests it to reduce the risk for future missions. Since DS2 probes' contain first-of-a-kind instruments and systems, "just getting them to the launch pad was a measure of success," said Gavit. Review boards will be set up within NASA and JPL to study the cause of the apparent loss and explore ways to prevent a recurrence.