The spot was chosen for the exploratory excavation after forensic technology and a cadaver-seeking police dog indicated disturbed soil and evidence of decomposition, said Sgt. Jeff Hollowell of the Inyo County Sheriff's Department, which was overseeing the investigation.
The evidence on its own is not proof there is a human body in the ground - or that any bodies found are connected to Manson and his followers.
But the combination of science and police work was strong enough to warrant the exploratory excavation, according to the crew conducting the two digs planned over three days.
"The evidence is indicative enough to where we're out here today," said Arpad Vass, senior researcher at the Oak Ridge National Laboratory, an expert in identifying and analyzing the chemicals exuded by human bodies as they break down.
The nearly 20 scientists, law enforcement officials and National Park rangers are camping in the high desert mountains bordering Death Valley for the duration of the dig.
The rugged terrain, accessible only by four-wheel drive vehicles able to climb over sharp rock and loose gravel, and the temperature, which hovered around 105 degrees, made the work hard for those involved. The nature of the soil - dry and chocked with rocks - made it difficult to operate some of the new forensic tools being put to work on this project, some for the first time on a case outside the laboratory, researchers said.
But investigators and forensic experts involved in re-examining the 40-year-old crime scene were anxious to see the results.
"We've got a lot riding on this," said Mammoth Lakes Police Sgt. Paul Dostie, who handled the cadaver-seeking dog that initially identified the suspect sites. "We have the science and law enforcement coming together, and this is a first. We're really looking to see how all these technologies come together."
Before the dig started Tuesday, the forensic expert had scanned the dirt with ground-penetrating radar and laser technology that highlights bones, as well as performed soil chemical analysis tests - all methods not available when Manson and his followers were arrested.
The National Park Service has closed the ranch to the public for the duration of the dig.
For years, rumors have swirled about more possible Manson victims - hitchhikers who visited the ranch and were not seen again, and runaways who drifted into the camp, then fell out of favor.
Manson and his followers hid at the ranch after the murders of actress Sharon Tate and six other people. He is serving a life sentence at Corcoran State Prison.
