Once more, with feeling: Dawn to take a closer look at Ceres

Meanwhile on Mars, we've found a twisted tail

Mars' twisty magnetic tail
NASA visualisation of Mars' twisted magnetotail. Image: Anil Rao/Univ. of Colorado/MAVEN/NASA GSFC

NASA's Dawn spacecraft has received another reprieve, with its mission to dwarf planet Ceres extended for another, closer, flyby.

The probe has orbited Ceres since March 2015 and has already revealed a 4,000 metre high mountain that's evidence of cryovolcanism on the dwarf planet.

The science is good enough – as is Dawn's condition – that the agency wants to take a closer look at Ceres next year.

NASA announced the second extension of the mission on Friday (October 20), and says the flight team is “studying ways to manoeuvre Dawn into a new elliptical orbit, which may take the spacecraft to less than 120 miles (200 kilometres) from the surface of Ceres at closest approach”.

Its closest prior approach was 240 miles (385 km).

While a closer approach makes for more detailed photography, the mission's focus will to gather data from Dawn's gamma ray and neutron spectrometer, to get a better understanding of how much ice is in Ceres' uppermost layer.

Dawn will be present when Ceres reaches perihelion, the closest approach to the sun, so the boffins expect to see ice on the surface turning to liquid and vapour.

The probe will run out of hydrazine late next year, after which it will remain in its final orbit rather than risking contaminating Ceres by crashing into it.

Meanwhile on Mars ... MAVEN spots a twisty magnetic tail

NASA's other big news from last week came from its Mars MAVEN mission: like Earth and Venus, the Red Planet has a magnetic tail following its orbit, but unlike its peers, Mars' is twisted by interaction with the solar wind.

The agency explained: “The team found that a process called 'magnetic reconnection' must have a big role in creating the Martian magnetotail because, if reconnection were occurring, it would put the twist in the tail.”

NASA Goddard's Gina DiBraccio said the strange tail was predicted by modelling: “Our model predicted that magnetic reconnection will cause the Martian magnetotail to twist 45 degrees from what’s expected based on the direction of the magnetic field carried by the solar wind”.

The recombination that twists the tail could also be helping strip Mars of its atmosphere: “Since the Martian magnetotail is formed by linking surface magnetic fields to solar wind fields, ions in the Martian upper atmosphere have a pathway to space if they flow down the magnetotail”, the NASA release notes. ®

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