Is NASA going to send astronauts to Mars?
That's the agency's stated goal, though there's no mission yet, certainly no budget (it would probably give legislators the jitters) and, at the moment, NASA doesn't have the technology to land astronauts safely and then bring them back to Earth.
So humans to Mars is aspirational, with the tough logistical and political issues yet to be resolved.
Amplification of NASA's long-term Mars strategy came on Monday at the start of a three-day conference at George Washington University in Washington called the Humans to Mars Summit, or H2M.
NASA administrator Charles Bolden was the keynote speaker and he was soon followed by senior agency officials who have Mars on the mind.
All expressed cautious optimism that the agency is on the right path to get to Mars eventually, though some members of the audience were openly impatient and more than a little dismissive of NASA's current plan to send astronauts on a mission to inspect a lassoed asteroid.
After three senior NASA officials - William Gerstenmaier, John Grunsfeld and Michael Gazarik, the associate administrators for human exploration, science and space technology, respectively - talked extensively of the asteroid mission, an audience member took a microphone and expressed exasperation that they were so focused on the asteroid rather than Mars.
Another member of the audience, Robert Terry, a retired physicist, made a reference to a private venture, Mars One, that vows to create a permanent Mars colony in just a decade
"When Mars One puts boots on the ground in 2023, what lessons do you expect you'll be learning from that?" he asked.
The officials declined to be combative, though Mr Gazarik, for one, noted that he was sceptical of some of the ambitious Mars missions being promoted by private groups. He added, in a conciliatory tone: "I'm sceptical of our own plans."
Then, as they were preparing to leave the stage, they received a nudge from the stage itself, when Artemis Westenberg, the president of Explore Mars - the nonprofit organisation that staged the conference - announced that her organisation had surveyed Americans and found that only 14 per cent favour a visit to an asteroid.
She quoted favourably a line from one of the asteroid-mission sceptics: "Why stand on a rock when you can walk on a world?"
But Mr Bolden, in kicking off the conference, made it clear the administration planned to take Mars one step at a time, starting with the development of a "commercial crew" program in which private companies would taxi American astronauts to the international space station.
Only if that program was fully funded by Congress could NASA turn to the harder tasks of sending astronauts on deep-space missions, he said.
He acknowledged that people in the audience wanted to go to Mars immediately.
"I don't know about you, but I'm not ready," he said. "I don't have the capability to do it. NASA doesn't have the capability to do that right now. But we're on a path to be able to do it in the 2030s."
The Obama administration's 2010 "National Space Policy of the United States of America" requires the NASA administrator to set "far-reaching exploration milestones", including: "By 2025, begin crewed missions beyond the moon, including sending humans to an asteroid. By the mid-2030s, send humans to orbit Mars and return them safely to Earth."
So, taken literally, the policy does not call for NASA to put astronauts on the surface of the fourth rock from the sun. They would go to Mars, take a close look from orbit, perhaps rendezvous with one of the small Martian moons, and come zooming home.
That may seem like a long way to go without bothering to land, but landing on Mars is extraordinarily difficult.
Mars has a very thin atmosphere, and without air, it's hard to brake a spaceship coming in at 21,000 kilometres per hour. Getting to Mars would be relatively easy if you were allowed to crash into it. Surviving will cost you extra.
"Can we do it? Yes," said Mr Gazarik, the head of space technology at NASA, speaking in advance of the H2M conference. But he quickly added: "It depends on your level of risk. You can send people many places. It is a question of risk."
And we needed new technology, he said. Finding ways to protect astronauts from deadly radiation in space is a major challenge. So is avoiding those crash landings: "We need better ways to slow down."
NASA succeeded last summer in landing the Curiosity rover within 2.5 kilometres of its target on Mars after a 560 million kilometre journey. The entry and descent used a novel method that included using a 4.5 metre diameter heat shield to slow down the craft, then a parachute, then chemical rockets. But landing a spaceship with astronauts would probably require a payload about 40 times heavier, Mr Gazarik said.
"That was a metric tonne. That was the size of a Mini Cooper. Imagine if we had a larger spacecraft, if we had fuel and a rocket to get off the planet," he said.
One possibility would be landing the fuel, the return rocket and the astronauts separately so that the payloads could be smaller. But that is easier said than done.
"You have got to land it all near the same place. It pushes on our ability to land accurately," Mr Gazarik said.
Top NASA officials have made clear that they see humans to Mars as the logical ambition for the agency.
In response to a reporter's request for clarification about the National Space Policy, an agency spokesman, Allard Beutel, said in an e-mail: "That's the written policy, which we generally refer to as 'going to Mars', but obviously we're looking at landing on Mars in the coming years, not just orbiting it. And before that is an asteroid mission.
"So, we have a number of incremental steps and missions ahead of us that will get better defined as we prepare to go to Mars."
There are private entrepreneurs who also want to send humans to Mars and who might be willing to accept far more risk than a program run by the US civilian space agency. But physics is the same for private and public explorers alike.
No one knows how much a human mission to Mars would cost. But in a time of pinched budgets, it's an ambitious goal for the space agency even when using imaginary future dollars.
Simply discussing potential costs could be problematic. The agency well remembers what happened in 1989, when President George H.W. Bush announced an ambitious space strategy that included a permanent moon colony and then a human landing on Mars.
A rough estimate emerged from NASA that such a suite of missions would cost $US400 billion. Congress flinched, and the Bush 41 Mars mission soon evaporated.
Chris Carberry, executive director of Explore Mars, said he was optimistic that
NASA could pull off a manned mission to Mars if given the money.
"If NASA was directed to do it and provided the resources, they could definitely do it," he said. "The question is whether we have the political will to do it. It's more of a policy issue."
The H2M conference is co-sponsored by GWU's Space Policy Institute, perhaps the leading academic think tank with a focus on government efforts in space. And the program lists a bevy of corporate sponsors, including Boeing, Lockheed Martin and ATK.