https://phys.org/news/2018-11-huge-crater-greenland-impact-northern.html Paywall: advances.sciencemag.org/content/4/11/eaar8173 A 31 km wide crater in Northern Greenland has been hidden under a massive glacier, until now. Using new radar systems and older technologies, the authors document the existence of a newly found massive crater. Getting a date on the impact event is currently fuzzy. They estimate it occurred in the Pleistocene which is a lot of time. (circa 2,588,000 to 11,700 years ago, more than a 2 million year span) . They estimate the iron meteor was 1 km wide. If you have an interest in punctual paleoclimate changes, then this research project - down the road - may be an interesting read as the subsequent planned research continues. There is a potential debris field, not proven yet, that is the next object of interest for the researchers.