A tool equipped with small, diamond-shaped heads cut 2.7 millimeters deep into a tiny area of a sharply angled rock dubbed Adirondack, said Stephen Gorevan (search), a scientist handling some of Spirit's workload.
"We made some history here. We put the first planned hole on Mars," he said.
The circular hole, measuring about 45 millimeters wide, could give scientists clues to Mars' geologic past.
"The rock gave us a lot of resistance," Gorevan said. "We needed three hours to go this deep."
Spirit has spent more than a month on Mars as part of an $820 million mission that includes its twin, Opportunity, which is exploring another part of the planet.
Spirit was disabled by computer problems for more than two weeks but scientists said Friday they had repaired the problem. The rover drilled into the rock as it remained parked but was expected to begin roaming the rocky surface within the next few days.
Data and images from the rock were expected late Saturday.