Asked by: Simon Bartlett, Leicester
Discovered last October, ‘Oumuamua was the first object of interstellar origin found within the Solar System. It is a fascinating object; an elongated red rock about 230 metres long, by 35 metres wide, but its origin is a complete mystery. Radiometric dating has been used very successfully to date meteorites found on Earth and presumably could be useful for dating ‘Oumuamua too.
For such a study the rubidium-strontium or samarium-neodymium isotope ratios would normally be measured by mass spectrometer. Assuming that a sample of ‘Oumuamua could be returned to Earth uncontaminated, that there are sufficient quantities of the required isotopes present and that no physical processes have altered the isotope ratios since formation, a reasonable estimate of the age of ‘Oumuamua should be possible.