ExoMars Highlights Radiation Risk for Mars Astronauts

ExoMars orbiter and rover (Credit: ESA/ATG medialab)

BERLIN, Germany (ESA PR) — 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 radiation 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.

Trace Gas Orbiter instruments (Credit: ESA/ATG medialab)

On Earth, a strong magnetic field and thick atmosphere protects us from the unceasing bombardment of galactic cosmic rays, 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.

“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.

Dust devil tracks on Mars (Credit: ESA/ Roscosmos/ CaSSIS)

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 radiation risk 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.

“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.”

  • Robert G. Oler

    the whole mars thing is a well giant joke…

  • Jeff2Space

    What did they assume for the travel time to and from Mars?

    One way to mitigate this problem is to simply burn more fuel to get to and from Mars faster. Yet another reason that low cost to orbit is a prerequisite for a sane Mars mission.

  • Robert G. Oler

    we are decades from really having the technology and the experience to do any of the Mars stuff with humans (much less the money)…we need to figure out how to reduce travel times…and more shielding AND the micro gee issues

  • envy

    Go faster.

    There, I figured it out, and it only took 3 seconds not decades.

  • Robert G. Oler

    think harder…all that does is limit your exposure, it does nothing to save you from the flare that toast you

  • Robert G. Oler

    Imagine DearMoon is flying and all of a sudden massive solar flare…themodern day version of the Titanic…interest soars

  • Jeff2Space

    You do design the HAB so that a small room can be used as a radiation shelter. You put all your water tanks around the thing. Also, you orient the craft such that the fuel tanks are between you and the sun. You mitigate the risk as best you can.

    But the fact is there are no guarantees in life! We’ve had many astronauts die over the years in accidents unrelated to space travel, so the only thing that’s truly certain about anyone’s life is that they will die. Dying for something you believe in is commendable, IMHO.

    So, you inform the astronauts of the risks and you let them decide if they want to go. Hint: There will always be far more volunteers to go on space missions than there will be opportunities.

  • Paul451

    Also, you orient the craft such that the fuel tanks are between you and the sun.

    Solar particulate radiation isn’t highly directional. It becomes more and more isotropic as you move away from the sun.

  • windbourne

    Supposedly, SX and NASA are working on nuke engines. That would change everything. Otherwise, it really should be a one way trip.

  • windbourne

    Yes, and when man lands on the moon, they will sink in 20-30′ of dust and die.

  • windbourne

    Spot on.

  • therealdmt

    Re:” 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.”

    This is actually better than some have feared.

    It shows a Mars trip can be done within current rad limits (although exposure on Mars itself will be an issue — not much use in going there if you can’t do Marswalks).

    Mars may well be a once-in-a-lifetime trip, but it looks like radiation may not be a showstopper.

    And remember, this was without even getting into mitigation strategies (such as, as mentioned by others, shielding the craft with the water for the trip, but also the human waste that will accumulate (yup, poo), and simply flying faster — as Musk plans to do). Surface ops may involve more shielded MarsVans with robot arms than tons of walking around in MarsSuits

  • therealdmt
  • Robert G. Oler

    we are quite certain of the radiation, this is what science is about.

  • Robert G. Oler

    how about you design the entire ship so that it can deal with this type of problem 🙂

  • Jeff2Space

    Because radiation shielding is *heavy*. Water, liquid methane, polyethylene, and etc. make for good shielding due to the large amount of hydrogen in them.

  • Jeff2Space

    NASA isn’t spending serious money on nuclear thermal engines (the only thing nuclear they’re spending money on is tiny nuclear reactors to use on the surface of the moon and/or Mars.

    SpaceX isn’t spending any money on nuclear because with refueling they simply do not need it. Chemical propulsion is “good enough” when you use liquid methane/LOX and plan on refueling (both in LEO and on Mars using in situ fuel manufacturing). And on Mars, they plan on using solar panels for power.

  • Jeff2Space

    We are quite certain of the radiation environment, which is why we can easily work around the problem via engineering.

  • Zed_WEASEL

    There is a radiation shelter aboard the BFS.

  • Robert G. Oler

    OK that takes care of the “killer” events but not of the normal radiation environment which is far far more deadly than on earth