ExoMars highlights radiation risk for Mars astronauts, and watches as dust storm subsides

September 19, 2018, European Space Agency

Artist’s impression of the ExoMars 2016 Trace Gas Orbiter (TGO) with its instrument packages labelled. Credit: ESA/ATG medialab
Astronauts on a mission to Mars would be exposed to at least 60% of the total radiation dose limit recommended for their career during the journey itself to and from the Red Planet, according to data from the ESA-Roscosmos ExoMars Trace Gas Orbiter being presented at the European Planetary Science Congress, EPSC, in Berlin, Germany, this week.

The orbiter's camera team are also presenting new images of Mars during the meeting. They will also highlight the challenges faced from the recent dust storm that engulfed the entire planet, preventing high-quality imaging of the surface.

Radiation monitoring

The Trace Gas Orbiter began its science mission at Mars in April, and while its primary goals are to provide the most detailed inventory of martian atmospheric gases to date – including those that might be related to active geological or biological processes – its monitor has been collecting data since launch in 2016.

The Liulin-MO dosimeter of the Fine Resolution Epithermal Neutron Detector (FREND) provided data on the radiation doses recorded during the orbiter's six-month interplanetary cruise to Mars, and since the spacecraft reached orbit around the planet.

On Earth, a strong magnetic field and thick atmosphere protects us from the unceasing bombardment of , fragments of atoms from outside our Solar System that travel at close to the speed of light and are highly penetrating for biological material.

In space this has the potential to cause serious damage to humans, including radiation sickness, an increased lifetime risk for cancer, central nervous system effects, and degenerative diseases, which is why ESA is researching ways to best protect astronauts on long spaceflight missions.

The ExoMars measurements cover a period of declining solar activity, corresponding to a high radiation dose. Increased activity of the Sun can deflect the galactic cosmic rays, although very large solar flares and eruptions can themselves be dangerous to astronauts.

Artist’s impression of the ExoMars 2020 rover (foreground), surface science platform (background) and the Trace Gas Orbiter (top). Not to scale. Credit: ESA/ATG medialab
"One of the basic factors in planning and designing a long-duration crewed mission to Mars is consideration of the radiation risk," says Jordanka Semkova of the Bulgarian Academy of Sciences and lead scientist of the Liulin-MO instrument.

"Radiation doses accumulated by astronauts in interplanetary space would be several hundred times larger than the doses accumulated by humans over the same time period on Earth, and several times larger than the doses of astronauts and cosmonauts working on the International Space Station. Our results show that the journey itself would provide very significant exposure for the astronauts to radiation."

The results imply that on a six-month journey to the Red Planet, and assuming six-months back again, an astronaut could be exposed to at least 60% of the total radiation dose limit recommended for their entire career.

The ExoMars data, which is in good agreement with data from Mars Science Laboratory's cruise to Mars in 2011–2012 and with other particle detectors currently in space – taking into account the different solar conditions – will be used to verify radiation environment models and assessments of the to the crewmembers of future exploration missions.

A similar sensor is under preparation for the ExoMars 2020 mission to monitor the radiation environment from the surface of Mars. Arriving in 2021, the next mission will comprise a rover and a stationary surface science platform. The Trace Gas Orbiter will act as a data relay for the surface assets.

Global dust storm subsides

Radiation is not the only hazard facing Mars missions. A global dust storm that engulfed the planet earlier this year resulted in severely reduced light levels at the surface, sending NASA's Opportunity rover into hibernation. The solar-powered rover has been silent for more than three months.

Orbiting 400 km above the surface, the ExoMars Trace Gas Orbiter's Colour and Stereo Surface Imaging System, CaSSIS, has also suffered. Because the surface of the planet was almost totally obscured by dust, the camera was switched off for much of the storm period.

Dust obscures surface of Mars. Credit: ESA/Roscosmos/CaSSIS, CC BY-SA 3.0 IGO
"Normally we don't like to release images like this (right), but it does show how the dust storm prevents useful imaging of the surface," says the camera's Principal Investigator, Nicolas Thomas from the University of Bern. "We had images that were worse than this when we took an occasional look at the conditions, and it didn't make too much sense to try to look through 'soup'."

But the camera team discovered that even a dust cloud has a silver lining.

"The dust-obscured observations are actually quite good for calibration," says Nicolas. "The camera has a small amount of straylight and we have been using the dust storm images to find the source of the straylight and begin to derive algorithms to remove it."

Since 20 August, CaSSIS has started round-the-clock imaging again.

"We still have some images affected by the dust storm but it is quickly getting back to normal and we have already had a lot of good quality images coming down since the beginning of September," adds Nicolas.

One image acquired on 2 September (shown here at the top of the page), although not completely free from artefacts, shows striking dark streaks that might be linked to the storm itself. A possible interpretation is that these features were produced by 'dust devils' – whirlwinds – stirring up loose surface material. The region, Ariadne Colles in the southern hemisphere of Mars, was imaged by NASA's Mars Reconnaissance Orbiter camera in March, before the storm, and there seemed to be little evidence of these streaks.

"We are very excited to be discussing some of the first scientific results from the ExoMars Trace Gas Orbiter at EPSC this week, as well as the progress of the upcoming surface mission," says Håkan Svedhem, ESA's Trace Gas Orbiter project scientist.

"While our instrument teams are working hard analysing the details of the atmospheric gas inventory and preparing these results for publication, we are certainly pleased to already be able to contribute to topical discussions on the dust storm and on issues that are essential for future crewed missions to Mars."

Explore further: Image: Frosty crater on Mars

Related Stories

Image: Frosty crater on Mars

September 18, 2018

This image shows the south-facing rim of a pit crater at 68°S in the Sisyphi Planum region of Mars. It is a colour composite made from images acquired on 2 September 2018 by the Colour and Stereo Surface Imaging System, ...

Image: Mars dust storm

July 20, 2018

The high resolution stereo camera on board ESA's Mars Express captured this impressive upwelling front of dust clouds – visible in the right half of the frame – near the north polar ice cap of Mars in April this year.

Red Planet rover set for extreme environment workout

May 30, 2018

A representative model of the ExoMars rover that will land on Mars in 2021 is beginning a demanding test campaign that will ensure it can survive the rigours of launch and landing, as well as operations under the environmental ...

ExoMars orbiter images Phobos

December 7, 2016

The ExoMars Trace Gas Orbiter has imaged the martian moon Phobos as part of a second set of test science measurements made since it arrived at the Red Planet on 19 October.

Recommended for you

Researchers investigate the peculiar radio source IC 1531

October 17, 2018

An international team of researchers has investigated a peculiar extragalactic radio source known as IC 1531. The new study analyzes the nature of IC 1531's high-energy emission, suggesting that the source is a radio galaxy. ...

Astronomers find a cosmic Titan in the early universe

October 17, 2018

An international team of astronomers has discovered a titanic structure in the early Universe, just two billion years after the Big Bang. This galaxy proto-supercluster, nicknamed Hyperion, is the largest and most massive ...

Double dust ring test could spot migrating planets

October 17, 2018

New research by a team led by an astrophysicist at the University of Warwick has a way of finally telling whether newly forming planets are migrating within the disc of dust and gas that typically surrounds stars or whether ...

Magnetic fields may be the key to black hole activity

October 17, 2018

Collimated jets provide astronomers with some of the most powerful evidence that a supermassive black hole lurks in the heart of most galaxies. Some of these black holes appear to be active, gobbling up material from their ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.