To better understand the human health risks of future missions to Mars, NASA and its international space station partners are considering flying as many as half a dozen additional one-year missions to the station, a NASA official said April 23.

Speaking at the Humans to Mars Summit in Washington, Bill Paloski, manager of NASA’s Human Research Program, said discussions are ongoing to fly up to six one-year crew increments after the first one-year increment, featuring NASA astronaut Scott Kelly and Roscosmos cosmonaut Mikhail Korniyenko and scheduled to start next March. If approved, the first of the additional one-year missions would likely start a year after the end of the first.

The purpose of the additional one-year missions would be to build up a larger database of the medical effects of long-term spaceflight to support planning for Mars missions, which could last up to two and a half years. “The way to extrapolate to 30-month missions is to get some more data at 12 months and to be able to determine that, between 6 months and 12 months, we’re able to protect people,” he said.

Those later one-year missions would, like the upcoming one, involve two crew members, Paloski said in an interview at the conference. One would be a Russian cosmonaut, and the other would either be a NASA astronaut or one from Europe, Japan or Canada. He added that they are not currently considering flying crew increments of longer than one year.