ISOCHRON (spacecraft)

[2] There is a stretch of nearly 2 billion years of lunar history that planetary scientists have not been able to date because the Apollo missions did not retrieve any young rocks.

[1] Lunar mare basalts formed through partial melting of the mantle, thus serve as probes of the structure and composition of the interior.

[2] The stated scientific objective of the mission is: "[To] make high-precision radiometric age measurements on these relatively young basalts to fill the existing gap in age-correlated crater size-frequency distributions (CSFDs), thereby greatly improving this widely-used tool for estimating the ages of exposed surfaces on rocky bodies.

"[2] The proposed ISOCHRON mission concept would have a robotic lander land just south of Aristarchus plateau and retrieve about 150 g (5.3 oz) of a basalt sample estimated to be 1.5 to 2.0 billion years old.

[1] The sample would be obtained from the Aristarchus plateau, located in the midst of the Oceanus Procellarum, a large expanse of lunar mare.