31.   The spacecraft is equipped with instruments designed to map the mineral composition of the rugged Martian surface, search for evidence of underground water and measure radiation levels.

32.   The U.S. spacecraft was on course to converge with the Russian outpost late Friday.

33.   The spacecraft is the Far Ultraviolet Spectroscopic Explorer, or FUSE, operated for NASA by the Johns Hopkins University.

34.   The two spacecraft are to remain docked until early Tuesday, permitting an exchange of crew members, equipment and supplies as well as joint medical research.

35.   Two other spacecraft are ready for liftoffs in the next month.

36.   Light-driven spacecraft will be slow to accelerate, but with time should reach velocities that will make travel across great distances possible.

37.   Previously, only manned spacecraft had been capable of completing such a feat.

38.   Solar-driven spacecraft will be slow to accelerate, but with time should reach velocities that will make travel across great distances possible.

39.   Solar-driven spacecraft would be slow to accelerate, but with time should reach velocities that would make travel across great distances possible.

40.   That means spacecraft can be smaller, lighter and less expensive to launch into space.