First of all, they have to have survived the impact. Laboratory tests have shown that frozen specimens of the Hypsibius dujardini species travelling at 3,000 km/h in a vacuum were fatally damaged when they smashed into sand. However, they survived impacts of 2,600 km/h or less – and their “hard landing” on the Moon, unwanted or not, was far slower.
The Moon’s surface is not protected from solar particles and cosmic rays, particularly gamma rays, but here too, the tardigrades would be able to resist. In fact, Robert Wimmer-Schweingruber, professor at the University of Kiel in Germany, and his team have shown that the doses of gamma rays hitting the lunar surface were permanent but low compared with the doses mentioned above – 10 years’ exposure to Lunar gamma rays would correspond to a total dose of around 1 Gy.
But then there’s the question of “life” on the Moon. The tardigrades would have to withstand a lack of water as well as temperatures ranging from −170 to −190°C during the lunar night and 100 to 120°C during the day. A lunar day or night lasts a long time, just under 15 Earth days. The probe itself wasn’t designed to withstand such extremes and even if it hadn’t crashed, it would have ceased all activity after just a few Earth days.