Two scientists in spacesuits, stark white against the auburn terrain of desolate plains and dunes, test a geo-radar built to map Mars by dragging the flat box across the rocky sand. When the geo-radar stops working, the two walk back to their all-terrain vehicles and radio colleagues at their nearby base camp for guidance. They can't turn to their mission command, far off in the Alps, because communications from there are delayed 10 minutes.

But this isn't the red planet it's the Arabian Peninsula. The desolate desert in southern Oman, near the borders of Yemen and Saudi Arabia, resembles Mars so much that more than 200 scientists from 25 nations chose it as their location for the next four weeks, to field-test technology for a manned mission to Mars. Public and private ventures are racing toward Mars both former President Barack Obama and SpaceX founder Elon Musk declared humans would walk on the red planet in a few decades.

New challengers like China are joining the United States and Russia in space with an ambitious, if vague, Mars program. Aerospace corporations like Blue Origin have published schematics of future bases, ships and suits.

The successful launch of SpaceX Falcon Heavy rocket this week "puts us in a completely different realm of what we can put into deep space, what we can send to Mars," said analog astronaut Kartik Kumar. The next step to Mars, he says, is to tackle non- engineering problems like medical emergency responses and isolation. "These are things I think can't be underestimated." Kumar said.

While cosmonauts and astronauts are learning valuable spacefaring skills on the International Space Station and the US is using virtual reality to train scientists the majority of work to prepare for interplanetary expeditions is being done on Earth. And where best to field-test equipment and people for the journey to Mars but on some of the planet's most forbidding spots?

Seen from space, the Dhofar Desert is a flat, brown expanse. Few animals or plants survive in the desert expanses of the Arabian Peninsula, where temperatures can top 125 degrees Fahrenheit, or 51 degrees Celsius. On the eastern edge of a seemingly endless dune is the Oman Mars Base: a giant 2.4-ton inflated habitat surrounded by shipping containers turned into labs and crew quarters.There are no airlocks.

The desert's surface resembles Mars so much, it's hard to tell the difference, Kumar said, his spacesuit caked in dust. "But it goes deeper than that: the types of geomorphology, all the structures, the salt domes, the riverbeds, the wadis, it parallels a lot of what we see on Mars."

The Omani government offered to host the Austrian Space Forum's next Mars simulation during a meeting of the United Nation's Committee On the Peaceful Uses of Outer Space. Scientists from across the world sent ideas for experiments and the mission, named AMADEE-18, quickly grew to 16 scientific experiments, such as testing a "tumbleweed" whip-fast robot rover and a new spacesuit called Aouda.

The cutting-edge spacesuit, weighing about 50 kilograms, is called a "personal spaceship" because one can breathe, eat and do hard science inside it. The suit's visor displays maps, communications and sensor data. A blue piece of foam in front of the chin can be used to wipe your nose and mouth.

"Terrestrial analogs are a tool in the toolkit of space exploration, but they are not a panacea," said Scott Hubbard, known as "Mars czar" back when he lead the US space agency's Mars program. The European Space Agency's list of "planetary analogues" includes projects in Chile, Peru, South Africa, Namibia, Morocco, Italy, Spain, Canada, Antarctica, Russia, China, Australia, India, Germany, Norway, Iceland, and nine US states. Next Thursday, Israeli scientists are to run a shorter simulation in a nature preserve called D Mars.