Scientists have first discovered that the “megaripples” on Mars – the huge sand waves observed on the surface of Mars – are moving structures, not ancient relics stuck in place since the ancient past of the Red Planet.
Megaripples, which also occur in deserts on Earth, are usually larger than smaller ripples of sand and are composed of thicker, coarser sand grains, which are located at the top of their ridges and rest on finer grains buried at the bottom.
The height of the ridge grains – combined with the very thin and weak winds of Mars’ light atmosphere – scientists considered these sedimentary structures to be static and immobile formations. This is not the case, new research shows.
A study by planetary scientist Simone Silvestro of the INAF Capodimonte astronomical observatory in Italy reveals that Martian megaripples are, after all, a flowing phenomenon ̵1; although you have to watch them very closely, you have to watch them closely.
By comparing images taken with a HiRISE (High Resolution Imaging Experiment) camera on NASA’s MARS reconnaissance orbit over several years, New Year’s Eve team found that Martin’s megaripples were definitely in motion, just in very slow motion.
Between 2007 and 2016, megaripples in two locations on Mars – Nili Fossae and McLaughlin Crater – moved at an average rate as low as 12 centimeters (4.7 inches) per year, with a maximum recorded rate of 19 centimeters (7.5 inches) per year.
At such slow displacement speeds, it is not surprising that these shifting sands were considered static – and previous comparisons, which examined formations in shorter time frames of only two to three Martian years, failed to detect gentle migration. Fortunately, we now have more data from the probes to take a closer look at what’s going on.
“We had the opportunity to see how these megarips move, because we now have more than 10 years of observation,” Silvestro explained to Inside Science.
However, it is not just our image probe that is expanding. We also understand what is possible in the Martian atmosphere, because previously scientists did not think that in a thin atmosphere, the winds of Mars would be strong enough to move megaripples – so large that they were up to 35 meters apart. (115 ft) apart in the study areas (although the diameter is about 5 meters or 16 feet).
The Martian wind seems to be able to move megaripples provided it has some help. Scientists suggest that the proximity of larger sand dunes located in the area of the Nili Fossae and McLaughlin craters could help shift the megaripple, while the fine-grained dunes provide a large volume of sand flow that can help move coarse grains at the top of the megaripple ridge.
Without such a degree of “impact” from the neighboring salt dunes, other Martian megaripples would not be able to move as fast or as fast as a fast-paced game would see.
Although these megaripples may be slow, the fact that we see them moving at all is not only a significant increase in our knowledge of the atmospheric conditions on Mars – it is also just some very impressive scientific work.
As planetary scientist Ralph Lorenz of Johns Hopkins University, who did not participate in the research, he said science“Now we can measure processes on the surface of another planet that are only a few times faster than our hair is growing.”
The findings are set out in Journal of Geophysical Research: Planets.