A search has been launched in Central Australia for a missing German couple after a park ranger realised the car the tourists rented had been parked for two days.

Northern Territory Police said the vehicle which the 76-year-old man and his 73-year-old wife hired was found in a carpark at Trephina Gorge, about 76 kilometres by road north-east of Alice Springs.

Earlier police said only one man was missing, but since reviewing CCTV footage of the couple hiring the car at Alice Springs Airport, they now say the man is accompanied by his wife.

A ground and air search began on Sunday after a ranger noticed footprints leading from the car and raised the alarm on Saturday night, Duty Superintendent Rob Burgoyne said.

They have since discovered two sets of footprints "some distance" from where the car was parked.

"We've got a jet ranger helicopter in the air with an observer on board, we've got five people on foot," Duty Superintendent Burgoyne said.

He said the police were concerned because of the couple's age, but recent rain in the area meant the pair have plenty of access to water.

"We're continuing the search, we're trying to locate next of kin just to inform them what's happened," he said.

"We're also trying to get medical information which may be of assistance just to let us know how the 76-year-old is travelling, as far as his medical conditions go."

Police said the couple arrived in the country earlier this month and hired the car on February 9.

Anyone with any information about the couple's whereabouts should contact police immediately.