An organisation led by Dennis Tito, the first ever space tourist, has announced its intention to launch a mission to Mars in 2018 - though just who or what will be on board remains to be seen.

Tito paid $20 million to be the first paying guest of the International Space Station in 2001, marking the start of the space tourism industry. Now he has formed the Inspiration Mars Foundation, which plans to launch “an historic journey to Mars and back in 501 days”, according to an announcement in advance of a press conference next Wednesday.

The announcement does not give many more details of the mission, but other speakers lined up for the press conference give some clues. Jonathan Clark of the National Space Biomedical Research Institute in Houston, Texas, a former NASA crew surgeon and recent advisor on Felix Baumgartner’s supersonic skydive from near the edge of space, will probably speak about the health risks of a long-term space mission, which hints at the possibility of a crewed mission.

Also speaking are Jane Poynter and Taber MacCallum of Paragon Space Development, a company with expertise in life support in extreme environments. The pair were both members of the Biosphere 2 mission, a controversial attempt at simulating a space colony two decades ago, and have previously proposed landing a greenhouse on the moon to grow flowers there.

Speculation ahead of the announcement is rife.

More: Short Sharp Science: First Space Tourist Plans Independent Mars Mission