The existing record for the longest consecutive space flight is 438 days by cosmonaut Valeri Polyakov,[39] and the most accrued time in space is 878 days by Gennady Padalka.[40] The longest time spent outside the protection of the Earth's Van Allen radiation belt is about 12 days for the Apollo 17 moon landing. This is minor in comparison to the 1100 day journey[41] planned by NASA as soon as the year 2028. Scientists have also hypothesized that many different biological functions can be negatively affected by the environment of Mars colonies.