For clues to Earth's climate, drill Mars

摘要

Digging a hole on another world may settle a nagging question about Earth's climate. From about 1300 to 1870, much of the Earth endured a long cold snap dubbed the Little Ice Age. The freeze is usually blamed on a dip in solar activity, but there are other suspects such as volcanoes. If the sun was responsible, we should see evidence of it across the solar system, says Ralph Lorenz of the Johns Hopkins University Applied Physics Lab in Laurel, Maryland. To settle the debate, he suggests digging a hole on Mars to see if it, too, had an ice age around that time (Icarus, doi.org/2g2). Temperature changes propagate downward through ice and soil, so a borehole will contain clues to past climate. The ice cap in Greenland contains signals of the Little Ice Age around 60 metres deep, for instance.