"I asked these people to do incredibly tough things, to push the limits," Goldin said in comments to reporters after addressing employees at the Pasadena facility.

"We were successful and I asked them to push harder. We were successful and I asked them to push harder and we hit a boundary. And I told them that they should not apologize. They did terrific things and I pushed it too hard. And thats why I feel responsible."

Goldins talk came in the wake of two reports released Tuesday that were sharply critical of how NASA ran its two Mars 98 missions, both of which failed late last year.

"We put them in a box there was no way out of, really," said John Casani, a JPL veteran who spearheaded the inquiry into the loss of the Polar Lander and its companion microprobes, Deep Space 2.

A second report, authored by Thomas Young, looked instead at NASAs overall Mars program. The report took NASA, JPL and industrial partner Lockheed Martin Astronautics to task for running a program that was under-funded, understaffed, overworked and that ran unacceptable risks.

"In my efforts to empower people I pushed too hard and, in doing so, stretched the system too thin," Goldin told JPL employees gathered in von Karman Auditorium. "It may have made some failure inevitable."

"We were successful and I asked them to push harder. We were successful and I asked them to push harder and we hit a boundary. And I told them that theyshould not apologize. They did terrific things and I pushed it too hard. And that's why I feel responsible."

But, Goldin said, he would not seek a NASA response that was punitive, prescriptive or that would seek to micromanage affairs at JPL or at Lockheed.

JPL is federally funded but, unlike other NASA centers, is managed by the California Institute of Technology, a private university. It is responsible for the lions share of NASAs deep space missions -- a role it has had since the Mariner 1 mission in 1962, its first attempt at a planetary spacecraft.

"When you have brilliant minds like you have at JPL, what you say is, Here is the problem, here is the challenge and I leave it to you to define it," Goldin said, essentially asking JPL to be its own "doctor" in analyzing its Mars program. Goldin added that the program should culminate in the landing of astronauts on the Red Planet.

David Baltimore, Caltechs president and a Nobel laureate in physiology and medicine, told JPL employees not to become complacent about risk, nor to lose their sense of audacity.

"One day we will look back on the Young report as a healthy midcourse correction in an exciting program of exploration," Baltimore said.