<p> But while the trip is technologically almost within grasp, experts say it’s probably still decades out because of funding uncertainties.
</p><p><strong>Mars is hard </strong></p><p> Wernher von Braun, the architect of the Apollo program, started work on a Mars mission right after the Moon landing in 1969, but the plan, like many after it, never got off the drawing board.
</p><p> What makes it so hard? For a start, the sheer distance.
</p><p> Astronauts bound for Mars will have to travel about 140 million miles (225 million kilometers), depending on where the two planets are relative to each other.
</p><p> That means a trip that’s many months long, where astronauts will face two major health risks: radiation and microgravity.
</p><p> The former raises the lifetime chances of developing cancer while the latter decreases bone density and muscle mass.
</p><p> If things go wrong, any problems will have to be solved on the planet itself.
</p><p><strong>’It’s the details’ </strong></p><p> That said, scientists have learned plenty of lessons from astronauts’ missions to the Moon and to space stations.
</p><p> “We have demonstrated on Earth orbiting spacecraft the ability for astronauts to survive for a year and a half,” said Jonathan McDowell, an astronomer for the Harvard–Smithsonian Center for Astrophysics.
</p><p> The general ideas of how to execute a Mars mission are in place, but “it’s the details” that are lacking, he added.
</p><p> One way to reduce the radiation exposure on the journey is getting there faster, said Laura Forczyk, the founder of space consulting firm Astralytical and a planetary scientist.
</p><p> This could involve using nuclear thermal propulsion which produces far more thrust than the energy produced by traditional chemical rockets.
</p><p> Another could be building a spacecraft with water containers strapped to it that absorb space radiation, said McDowell.
</p><p> Once there, we’ll need to find ways to breathe in the 95-percent carbon dioxide atmosphere. Perseverance has an instrument on board to convert carbon dioxide to oxygen, as a technical demonstration.
</p><p> Other solutions involve breaking down the ice at the planet’s poles into oxygen and hydrogen, which will also fuel rockets.
</p><p> Radiation will also be challenging on the planet, because of its ultra thin atmosphere and lack of a protective magnetosphere, so shelters will need to be well shielded, or even underground.
</p><p>Risk tolerance </p><p> The feasibility also comes down to how much risk we are willing to tolerate, said G. Scott Hubbard, NASA’s first Mars program director who’s now at Stanford.
</p><p> During the Shuttle era, said Hubbard, “the demand was that the astronauts face no more than three percent increased risk in death.”
</p><p> “They have now raised that — deep space missions are somewhere between 10 and 30 percent, depending on the mission, so NASA’s taking a more aggressive or open posture,” he added.
</p><p> That could involve raising the permissible level of total radiation astronauts can be exposed to over their lifetimes, which NASA is also considering, said Forczyk.
</p><p><strong>Political will </strong></p><p> The experts agreed the biggest hurdle is getting buy-in from the US president and Congress.
</p><p> “If humanity as a species, specifically the American taxpayer, decides to put large amounts of money into it, we could be there by the 2030s,” said McDowell.
</p><p> He doesn’t think that’s on the cards, but said he would be surprised if it happened later than the 2040s, a conclusion shared by Forczyk.
</p><p> President Joe Biden hasn’t yet outlined his Mars vision, though his spokeswoman Jen Pskai said this month the Artemis program had the administration’s “support.”
</p><p> Still, the agency is facing budget constraints and is not expected to meet its goal of returning astronauts to the Moon by 2024, which would also push back Mars.
</p><p><strong>SpaceX wildcard </strong></p><p> Could NASA be beaten to it by SpaceX, the company founded by billionaire Elon Musk, who is targeting a first human mission in 2026?
</p><p> Musk has been developing the next-generation Starship rocket for the purpose — though two prototypes blew up in spectacular fashion on their recent test runs.
</p><p> These might look bad, but the risks SpaceX is able to take, and NASA as a government agency can’t, gives it valuable data, argued Hubbard.
</p><p> That could eventually give SpaceX an edge over NASA’s chosen rocket, the troubled Space Launch System (SLS) which is beset by delays and cost overrun.
</p><p> But not even one of the richest people in the world can foot the entire bill for Mars themselves.
</p><p> Hubbard sees a public-private partnership as more likely, with SpaceX providing the transport and NASA solving the many other problems.
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