"As it stands today, we can't go to Mars, due to radiation," said physicist Marco Durante. "It would be impossible to meet acceptable dose limits." Scientists also worry about the impact on humans of a prolonged period of reduced gravity and isolation. Musk says the first travelers to Mars must be "prepared to die" on the Red Planet

NASA has plans for a craft it calls the Mars Ascent Vehicle (MAV).

NASA's timeline calls for a crewed mission to the moon by 2024, a lunar base by 2028, and flights from the moon base to Mars sometime in the 2030s

"The goal," said NASA Administrator Jim Bridenstine, "is to discover life on another world."

although the question isn't without controversy. The 1976 NASA mission discovered four samples that registered as positive for microbial respiration, but a subsequent test found no signs of organic matter

microbial life under the surface or that such life once existed there. Such a finding would be "extraordinary" and indicate life may exist in many other places in the universe, said Dr. Sarah Johnson, a planetary scientist at Georgetown University.

Have we found life?No

NASA concluded the fireworks on July 30 with Perseverance, designed to put the largest, most sophisticated rover yet on Mars.

China followed four days later with Tianwen-1

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