Rebecca Ward, Voice of America, November 10, 2003

The spacecraft Voyager 1 is still sending data back to NASA, the U.S. government space agency, after more than 26 years in space. It is now the most distant man-made object in space, traveling billions of kilometers from earth and perhaps reaching the outer edges of our solar system. Two teams of American scientists are reporting two different scenarios of the Voyager's latest adventures, although both teams agree that the spacecraft is in uncharted territory.

Space scientists believe the unmanned spacecraft, Voyager 1, is on the verge of reaching the outside of our solar system, beyond the sun's influence. Or perhaps, as at least one prominent professor says, it's already there. Just what kind of threshold Voyager has crossed is under debate. However, there is no question as to where it's headed. As Project Scientist Edward Stone explains, Voyager is going where no other spacecraft has gone before.

There is no conclusion on whether or not Voyager has actually passed the so-called "Termination Shock," where the spacecraft would encounter a dramatic drop in solar wind speed and an increase in interstellar plasma or particles. But according to the head of the space department at Johns Hopkins University, Stamatios (Tom) Krimigis, that has already happened. He says Voyager 1 crossed the threshold last year.

Mr. Krimigis is the leader of a team of scientists whose findings are published in this week's issue of the journal Nature.

On the other side of the debate is Frank McDonald of the University of Maryland whose teams' findings will also be published in Nature. He says the Voyager has been on an amazing ride, traveling 13.4 billion kilometers, but he does not believe it has reached the region of the "termination shock."

Mr. McDonald says he agrees with the observations of the Krimigis team, but his researchers interpret them differently. He says the Voyager is in the neighborhood of termination shock, just not over it.

Both teams of scientists note the drop in solar wind, which is believed to be one of the indicators of reaching the end of the solar system, but they give different explanations for the phenomenon. Keith Cowing of NASAWatch.com explains the discrepancy this way:

Mr. Cowing goes on to say that scientists have created this boundary where they believe the solar system ends, and interstellar space begins. "And what they're seeing is they've reached this point that they thought they've crossed this line," he said, "then they come back again and they're seeing some readings representative of interstellar influences but they're still seeing readings that represent what they would expect if the sun were still controlling the show, so as one scientist said, its nature doesn't seem to be cooperating with our models."

But whether or not Voyager 1 has reached the edge of the solar system, or still has a way to go, is not necessarily the main lesson from the team's findings. Mr. Cowing says scientists are gathering data from truly unknown territory and are scratching their heads over numbers being sent from a spacecraft that should have died 20 years ago.