Stressing that human exploration of Mars is on the horizon, NASA Administrator Jim Bridenstine has said that the agency is planning its first round-trip voyage to Mars to take about two years during which the crew could spend about a month on the Martian surface.The US space agency wants to send humans to Mars as early as the 2030s.NASA will use advanced propulsion systems to enable a faster journey to the Red Planet while limiting radiation exposure for its astronauts and other mission risks, Bridenstine said on Monday while participating in a discussion with the Space Foundation, a non-profit organisation."Our preferred launch window will give the crew about 30 days on the Martian surface, which is ample time to search for life on another world," he said."Other options could require crew to be on the surface for more than a year and away from Earth for as long as three years, but it will be a long time before we have the funding, technology, supplies, and capabilities to sustain such a mission," said Bridenstine.NASA plans to return humans to the Moon by 2024 under the Artemis programme."Our sights remain set on sending humans to Mars and the Artemis program will give us the experience living on another world closer to home," the NASA Administrator said."Artemis missions on and around the Moon will help us make our next giant leap while robots like the Perseverance rover pave the way for our first human explorers to Mars," he added.NASA is targeting July 30 for the launch of the Perseverance Mars rover from Cape Canaveral Air Force Station in Florida.Among the investigations onboard, the rover will carry two that will support future crewed missions to the fourth planet -- one to produce oxygen from the Martian atmosphere and another to aid in development of weather forecasting.The mission will also use new terrain navigation and landing technologies as well as study how a potential spacesuit material is affected by the Martian environment, Bridenstine noted.