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The planets are in a gravitational dance around the sun<\/p>\n
Shutterstock\/Johan Swanepoel<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n
The gravitational tug of Mars may be strong enough to stir up Earth\u2019s ocean, shifting its sediments as part of a 2.4-million-year climate cycle, researchers claim.<\/p>\n
It has long been accepted that wobbles in Earth\u2019s orbit around the sun influence the planet\u2019s climate, with these Milankovitch cycles operating on periods measured in thousands of years. Now, Adriana Dutkiewicz at the University of Sydney and her colleagues say they have found a new 2.4-million-year \u201cGrand Cycle\u201d, which they believe is driven by Mars and has had dramatic impacts on currents in Earth\u2019s oceans for at least 40 million years.<\/p>\n
The evidence for this cycle comes from almost 300 deep-sea drill cores that reveal unexpected variation in the deposition of ocean sediment. During periods of stable ocean currents, oceanographers expect sediment to settle in steady layers, but unusual currents and eddies can see it accumulate elsewhere.<\/p>\n
According to the team, absences or hiatuses in the sediment deposition record line up with times when Mars\u2019s gravity exerts maximum force on Earth, subtly impacting our planet\u2019s orbital stability. This changes solar radiation levels and climate, manifesting as stronger currents and eddies in the oceans.<\/p>\n
<\/p>\n Team member Dietmar M\u00fcller, also at the University of Sydney, acknowledges that the distance between Earth and Mars is so vast that it is hard to conceive of any significant gravitational force being exerted. \u201cBut there are so many feedbacks that can amplify even subtle changes,\u201d he says. \u201cMars\u2019s impact on Earth\u2019s climate is akin to a butterfly effect.\u201d<\/p>\n Benjamin Mills at the University of Leeds, UK, says the drill cores provide more evidence for the existence of \u201cmegacycles\u201d in global environmental change.<\/p>\n \u201cMany of us have seen these multi-million-year cycles in various different geological, geochemical and biological records \u2013 including during the famous explosion of animal life in the Cambrian Period,\u201d he says. \u201cThis paper helps cement these ideas as key parts of environmental change.\u201d<\/p>\n But Matthew England at the University of New South Wales in Sydney says that while he welcomes the work and thinks it adds to an understanding of climate cycles at a geological scale, he isn\u2019t convinced by the paper\u2019s conclusions.<\/p>\n \u201cI\u2019m sceptical of the link to Mars, given its gravitational pull on Earth is so weak \u2013 at only about one one-millionth of that of the sun,\u201d he says. \u201cEven Jupiter has a stronger gravitational field for Earth.\u201d<\/p>\n England also points out that even if Mars is having an influence, it is nothing compared with human-driven climate change. \u201cGreenhouse gas forcing is like a sledgehammer in comparison, so this has no bearing on present-day climate, where we are seeing melting ice sheets reduce the ocean overturning circulation.\u201d<\/p>\n Topics:<\/p>\n<\/section><\/div>\n