Earlier this week, Mars One announced that 100 candidates for the first Mars colony had been selected from an initial pool of 202,586 applicants. That announcement has generated hundreds of headlines to go along with many more featuring interviews with some of the final 100.

“The large cut in candidates is an important step towards finding out who has the right stuff to go to Mars. These aspiring martians provide the world with a glimpse into who the modern day explorers will be.” said Bas Lansdorp, Co-founder & CEO of Mars One, in a statement.

There have been discussions on why someone would want to take a one way trip to Mars as well as conversations with would be colonists about what they hope to accomplish. However, it has also been pointed out that selecting candidates is relatively easy compared to putting a permanent settlement on Mars.

Humans have little experience with manned deep space missions. The Apollo missions to the Moon have been our only real adventure outside the Earth’s protective magnetic field and the Moon is only outside that protective shell sometimes.

It is estimated that a trip to Mars would take six to eight months. It is not unusual for astronauts to spend about that long on the International Space Station however, six months in deep space is a bit more difficult and there are serious challenges to be met.

Outside of Earth’s magnetic field, astronauts will face intense solar radiation. Researchers are aware of this problem and are working on solutions, however there is no proven solution to protect astronauts at this point.

There will also be considerable physiological and psychological challenges facing the crew. These include isolation, a lengthy amount of time spent in a small space and the long term loss of muscle mass due to weightlessness.

After landing on Mars there will have to be plans in place to provide food, water and air for the astronauts. Mars One might save money by making it a one way mission, but providing food and water for the astronauts forever could be a challenge.

The health effects of the red dust on Mars is also unknown. The dust is what gives Mars its color and the name the Red Planet. The dust is red because it’s primarily composed of iron oxide, more commonly known as rust. No one knows what exposure to that much iron oxide over a prolonged period will do to people or the machinery that will be necessary to keep people alive.

NASA is working on all of these problems for their own manned Mars mission, scheduled for the 2030s. The estimated cost of this trip will be about $100 billion by the time its all done. Mars One claims that their mission will cost $6 billion and that is where many of the questions and criticisms about the program come in.

“Even a successful space start-up like SpaceX, which shares Mars One’s goal of reaching Mars, has only raised $1.2 billion in funding, and has likely not come close to earning $6 billion,” said Tim Fernholz in Quartz.

Mars One plans on financing their mission through donations as well as the exclusive rights to a reality TV show about the mission. It is unclear how well the not-for-profit is doing in accumulating donations, although they did fall short in a $400,000 Indiegogo campaign. They also do not appear to have a partner yet for the planned reality show and have been unsuccessful at selling rights to the round two interviews.

According to the stated timeline for Mars One, groups will start training in a Mars-outpost like simulation starting this year. According to Lansdorp the facility will be ready later this year, though the company has not announced a building site or revealed any further details on it to date.

In 2018, the schedule calls for Mars One to launch a communications satellite into orbit around Mars and put a robotic lander on the surface. However, construction hasn’t yet begun on either nor has a rocket been scheduled to carry them.

According to Spacenews, Surrey Satellite Technology Ltd. (SSTL) delivered a concept study for the satellite but has received no further instructions from Mars One about how to proceed. Lockheed Martin has likewise done a concept study on the lander but has yet to get a go-ahead to start building it.

So while it is likely that humans will eventually land on Mars and even build settlements there, it is not clear that the Mars One candidates should start packing just yet.