[meteorite-list] Radiation Measured by NASA's Curiosity on Voyage to Mars has Implications for Future Human Missions

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 30 May 2013 12:07:17 -0700 (PDT)
Message-ID: <201305301907.r4UJ7HZV023987_at_zagami.jpl.nasa.gov>

May 30, 2013

Trent J. Perrotto
Headquarters, Washington
trent.j.perrotto at nasa.gov

Deb Schmid
Southwest Research Institute, San Antonio
deb.schmid at swri.org

RELEASE: 13-165


WASHINGTON -- Measurements taken by NASA's Mars Science Laboratory
(MSL) mission as it delivered the Curiosity rover to Mars in 2012 are
providing NASA the information it needs to design systems to protect
human explorers from radiation exposure on deep-space expeditions in
the future.

MSL's Radiation Assessment Detector (RAD) is the first instrument to
measure the radiation environment during a Mars cruise mission from
inside a spacecraft that is similar to potential human exploration
spacecraft. The findings will reduce uncertainty about the
effectiveness of radiation shielding and provide vital information to
space mission designers who will need to build in protection for
spacecraft occupants in the future.

"As this nation strives to reach an asteroid and Mars in our
lifetimes, we're working to solve every puzzle nature poses to keep
astronauts safe so they can explore the unknown and return home,"
said William Gerstenmaier, NASA's associate administrator for human
exploration and operations in Washington. "We learn more about the
human body's ability to adapt to space every day aboard the
International Space Station. As we build the Orion spacecraft and
Space Launch System rocket to carry and shelter us in deep space,
we'll continue to make the advances we need in life sciences to
reduce risks for our explorers. Curiosity's RAD instrument is giving
us critical data we need so that we humans, like the rover, can dare
mighty things to reach the Red Planet."

The findings, which are published in the May 31 edition of the journal
Science, indicate radiation exposure for human explorers could exceed
NASA's career limit for astronauts if current propulsion systems are

Two forms of radiation pose potential health risks to astronauts in
deep space. One is galactic cosmic rays (GCRs), particles caused by
supernova explosions and other high-energy events outside the solar
system. The other is solar energetic particles (SEPs) associated with
solar flares and coronal mass ejections from the sun.

Radiation exposure is measured in units of Sievert (Sv) or
milliSievert (one one-thousandth Sv). Long-term population studies
have shown exposure to radiation increases a person's lifetime cancer
risk. Exposure to a dose of 1 Sv, accumulated over time, is
associated with a 5 percent increase in risk for developing fatal

NASA has established a 3 percent increased risk of fatal cancer as an
acceptable career limit for its astronauts currently operating in
low-Earth orbit. The RAD data showed the Curiosity rover was exposed
to an average of 1.8 milliSieverts of GCR per day on its journey to
Mars. Only about 5 percent of the radiation dose was associated with
solar particles because of a relatively quiet solar cycle and the
shielding provided by the spacecraft.

The RAD data will help inform current discussions in the United States
medical community, which is working to establish exposure limits for
deep-space explorers in the future.

"In terms of accumulated dose, it's like getting a whole-body CT scan
once every five or six days," said Cary Zeitlin, a principal
scientist at the Southwest Research Institute (SwRI) in San Antonio
and lead author of the paper on the findings. "Understanding the
radiation environment inside a spacecraft carrying humans to Mars or
other deep space destinations is critical for planning future crewed

Current spacecraft shield much more effectively against SEPs than
GCRs. To protect against the comparatively low energy of typical
SEPs, astronauts might need to move into havens with extra shielding
on a spacecraft or on the Martian surface, or employ other
countermeasures. GCRs tend to be highly energetic, highly penetrating
particles that are not stopped by the modest shielding provided by a
typical spacecraft.

"Scientists need to validate theories and models with actual
measurements, which RAD is now providing," said Donald M. Hassler, a
program director at SwRI and principal investigator of the RAD
investigation. "These measurements will be used to better understand
how radiation travels through deep space and how it is affected and
changed by the spacecraft structure itself. The spacecraft protects
somewhat against lower energy particles, but others can propagate
through the structure unchanged or break down into secondary

After Curiosity landed on Mars in August, the RAD instrument continued
operating, measuring the radiation environment on the planet's
surface. RAD data collected during Curiosity's science mission will
continue to inform plans to protect astronauts as NASA designs future
missions to Mars in the coming decades.

SwRI, together with Christian Albrechts University in Kiel, Germany,
built RAD with funding from NASA's Human Exploration and Operations
Mission Directorate and Germany's national aerospace research center,
Deutsches Zentrum fur Luft- und Raumfahrt.

NASA's Jet Propulsion Laboratory, a division of the California
Institute of Technology in Pasadena, Calif., manages the Mars Science
Laboratory Project. The NASA Science Mission Directorate at NASA
Headquarters in Washington manages the Mars Exploration Program.

For more information about the findings and the Mars Science
Laboratory mission, visit:


For more information about NASA human spaceflight and exploration,

Received on Thu 30 May 2013 03:07:17 PM PDT

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