In mid-March, NASA announced plans to move forward with its Asteroid Redirect Mission (ARM): a controversial mission to grab a piece of an asteroid, tow it into orbit around the moon, and then bring astronauts to it, sometime in the 2020s.
In a press conference on March 25, NASA provided new details on what the mission will look like: an uncrewed probe will land on a relatively large asteroid and grab a small boulder off it, then later rendezvous with an Orion capsule that is carrying the astronauts.
NASA bills this mission as a "stepping stone" to Mars — a test of the SLS rocket, solar electric propulsion, and other technology it hopes to use for an eventual human Mars mission. It hopes to launch the probe by December 2020, so the asteroid could be in place for the rendezvous by 2025 — a goal set out by President Obama a few years ago.
But shortly after the announcement, there was all sorts of criticism, with some space experts saying the "scaled-down" mission was a "wimp out," compared with an alternate option that would have involved capturing an entire asteroid in an inflatable bag. Since ARM was announced in 2013, in fact, there's been lots of opposition from both House Republicans and independent space experts who say the pricey mission (estimated to cost somewhere between $1.25 and $2.6 billion) doesn't really get us any closer to Mars.
So why exactly is NASA bent on carrying out this mission — and how did it become so controversial? It all goes back to the convoluted, politically driven decision-making process that birthed ARM in the first place.
NASA's plan to catch an asteroid
The actual mission plan, at least, is fairly straightforward. It'll start with the launch of an uncrewed probe on an Atlas V rocket in December 2020. After about two years, the probe will reach an asteroid, and over the course of another year or so it will survey its surface and locate a boulder to pick up.
NASA still hasn't finalized the target asteroid, but the agency has mentioned the asteroid 2008 EV5 — a 1,300-foot-wide chunk of rock — as a leading candidate, along with a pair of other asteroids named Itokawa and Bennu as possibilities. The probe would be capable of picking up a boulder roughly 13 feet in diameter.
The probe would then carry the boulder back toward Earth and enter the moon's orbit by 2025. NASA would launch an SLS rocket (currently in development) with an Orion capsule, carrying several astronauts on board. The capsule would link up with the probe in lunar orbit for several weeks, giving astronauts a chance to collect samples and data from the asteroid.
If the mission is actually carried out as planned, these astronauts will be the first people ever to make contact with an asteroid in orbit, and they'll have traveled farther from the Earth than anyone ever has before.
The asteroid mission is the result of a convoluted political process
The mission was originally devised as a compromise solution to a political dilemma. It goes back to 2010, when Obama killed the underfunded, overdue Constellation program — a plan, announced by George W. Bush, that would have returned astronauts to the moon's surface by 2020, and to Mars sometime afterward.
But lawmakers — especially those representing districts where Constellation programs provided jobs — fought the cancellation. Eventually, they saved several aspects of the program, including the Orion space capsule, and directed NASA to build a new rocket system (SLS) to replace the canceled one.
SLS, though, would need something to do. So Obama proposed landing humans on an asteroid in the 2020s as a "stepping stone" to Mars. But NASA still didn't have nearly enough funding for an ambitious trip to send humans to deep space and land them on an asteroid in orbit.
ARM was announced in 2013 as a cheaper solution. Instead of carrying astronauts all the way to an asteroid, an uncrewed probe would be used to grab the asteroid and put it in orbit around the moon — allowing NASA to technically meet Obama's goal within a realistic budget.
Such a mission would still involve a brand new destination for human space exploration — something NASA hasn't been able to say since landing on the moon in 1969. And in theory, the mission would allow NASA to develop technologies needed to carry out a crewed Mars mission with Orion and SLS later on, as well as systems that could someday help defend our planet from asteroids.
Politicians and scientists are critical of the asteroid mission
Not everyone has agreed with NASA's rosy assessment. In a 2014 report, the NASA Advisory Council (an independent group of experts) said it had "serious concerns" with some of NASA's plans.
Among other things, the council noted that ARM wouldn't provide the long-duration mission needed to help NASA learn how to keep astronauts alive in space for several years at a time. A simpler, cheaper mission not involving an asteroid could provide most of the same stepping-stone benefits. Planetary scientists, meanwhile, say the mission won't help them learn much about asteroids that they won't learn from other missions involving uncrewed probes.
Congressional Republicans have been especially critical of ARM, saying it's not a logical part of a plan to get to Mars and advocating for a return to the moon instead. "I love NASA. I’m devoted to NASA. But I don’t think pushing a rock around space is a productive use of their time and scarce resources," Representative John Culberson, a Texas Republican, said in an interview in 2013.
"It’s time the administration put forward an inspirational goal worthy of a great space-faring nation," Representative Lamar Smith, another Texas Republican and chair of the House committee on Science, Space, and Technology, wrote in an op-ed soon after ARM was announced. "The asteroid retrieval mission is not it."
As a result, ARM hasn't gotten any specified funding in any NASA budget passed so far. Last year, House Republicans went a step further, attempting to prohibit NASA from spending anything on the mission in early drafts of spending bills, though the language was deleted from the final drafts. No Democrat has spoken up as a strong supporter of ARM, either.
Even some die-hard space exploration advocates are skeptical of ARM. "We support the mission, conditionally, if NASA carries out an external cost estimate," Casey Dreier of the Planetary Society told me for an article last month. "But our conditional support has not been met."
NASA says the mission will cost $1.25 billion, not including the cost of the launch vehicle. Independent estimates peg it at $2.6 billion. Either way, it's a lot of money for a mission that in the eyes of many doesn't accomplish all that much.
So will the asteroid mission actually happen?
All this has led to repeated delays for ARM: NASA was originally planning on announcing these recent details last year, and still hasn't released a detailed budget. And the announcement that the mission will involve grabbing a boulder, instead of an entire asteroid, has led to a new round of criticism, with skeptics calling the mission a "bait and switch."
They have a fair point — and in retrospect, it might not be smart for us to orient our entire human spaceflight program around achieving a goal laid out as a talking point in a presidential speech. Especially when we need to resort to technicalities (bringing a piece of an asteroid to astronauts, instead of "sending astronauts to an asteroid," as Obama said) to do it.
But there are some good reasons to get excited about ARM. As Corey Powell points out at Discover, it will indeed allow NASA to develop propulsion systems that will help us better explore the solar system. Though it might not be as ambitious as visiting an asteroid in orbit, it'd still be an entirely new destination for humans — and one that's financially feasible.
In theory, taking astronauts to an asteroid in orbit would serve as a more effective stepping stone to Mars, but it'd cost way more money than NASA has to spend. As Powell puts it, "The choice isn’t between an asteroid or Mars; the choice is between an asteroid and nothing at all."
So will ARM actually happen? There's still some speculation it could be canceled, but the recent announcement is a sign that it could live. NASA is formally asking for $220 million to spend on ARM for its 2016 budget, but nothing's certain yet.
NASA is racing the clock if it wants to meet Obama's 2025 deadline. But in theory, NASA could design the probe over the next few years, launch it in 2020, and have the asteroid in place in 2025, when the SLS rocket and Orion capsule are ready to carry astronauts to visit it.
Read more: For NASA, sending a person to Mars is simple. Dealing with Congress is hard.WATCH: Can we colonize Mars?