Do you remember Siding Spring, the comet that closely buzzed Mars in 2014 under the watchful eye of seven orbiters and Martian rovers? It turns out Mars remembers it well. According to a new study using data from the Mars Atmosphere and Volatile EvolutioN Mission (MAVEN) spacecraft, the comet caused problems that NASA experts are describing as “chaos.”
Comet Siding Spring plunged the magnetic field around Mars into chaos. We think the encounter blew away part of Mars’ upper atmosphere, much like a strong solar storm would.
Jared Espley, a MAVEN science team member at NASA’s Goddard Space Flight Center in Maryland, said this in the study, published recently in Geophysical Research Letters. Comet Siding Spring (C/2013 A1) was just a .5 km (.3 mile) diameter ball of ice and rock that never got closer than 140,000 km (87,000 miles) from Mars. However, it’s coma – that fuzzy haze around the comet comprised of ice and dust – measured a million km (620,000 miles) in all directions.
The coma forms a magnetic field around the comet caused by interaction between charged plasma particles. That coma blasted Mars with charged particles for hours and the strongest part of the field – the area closest to the actual comet – reached the Martian surface.
This would not be a problem for Earth, whose magnetic field is strong because it’s generated from inside the planet, but it was definitely chaos for the weak Martian field. Siding Spring’s magnetic field actually overpowered and merged with it.
The effect was immediate. Charged particles in Mars’ magnetosphere began pointing in different directions. At the most intense part of the passing, the researchers say the Martian magnetic field actually flapped like a curtain in the wind. Espley compared it to a short-lived solar storm. The flapping created holes in the planet’s upper atmosphere, allowing gas to escape.
Can any good come from this chaos? Bruce Jakosky, MAVEN’s principal investigator, says yes.
By looking at how the magnetospheres of the comet and of Mars interact with each other, we’re getting a better understanding of the detailed processes that control each one.
Bottom line …. even a near-hit by a comet is bad news.