Posted on by Elizabeth Howell

How Much Radiation Would You Get During A Mars Mission?

An artist's conception of future Mars astronauts. Credit: NASA/JPL-Caltech

While asking questions about habitability on Mars, one thing that scientists also need to consider is whether it’s safe enough for humans to even do exploration there. Radiation is definitely a big factor — in a press conference yesterday (Dec. 9) for the American Geophysical Union’s conference, scientists said the environment is unlike anything we are used to naturally on Earth.

Radiation on Mars comes from two sources: galactic cosmic rays (over the long term) and solar energetic particles (in short bursts of activity when the sun gets super-active). Of note, the sun has had a muted peak to its solar cycle, so that’s affecting the expected amount of particles on Mars. But the Mars Curiosity rover, in its first 300 Earth days of roaming, has plenty of data on galactic cosmic rays.

On the Martian surface, the average dose is about 0.67 millisieverts (mSv) per day, at least between the measurement period of August 2012 and June 2013. The journey to Mars had a dose of 1.8 mSv per day inside the spaceship. So what does that means for NASA’s human health consideration concerns?

NASA's Mars rover Curiosity took this self-portrait, composed of more than 50 images using its robotic arm-mounted MAHLI camera, on Feb. 3. The image shows Curiosity at the John Klein drill site. A drill hole is visible at bottom left. Credit: NASA / JPL / MSSS / Marco Di Lorenzo / Ken Kremer- kenkremer.com
NASA’s Mars rover Curiosity took this self-portrait, composed of more than 50 images using its robotic arm-mounted MAHLI camera, on Feb. 3. The image shows Curiosity at the John Klein drill site. A drill hole is visible at bottom left. Credit: NASA / JPL / MSSS / Marco Di Lorenzo / Ken Kremer- kenkremer.com

With a 500-day trip on the surface and the journey to and from Mars (which would take 180 days each way), NASA is saying the total dosage for the mission would be about 1 Sv. Population studies over the long term have shown that increases the fatal cancer risk by 5%. Current NASA guidelines for low-Earth orbit don’t allow for a more than 3% increase, but 1 Sv is within the guidelines for several other space agencies.

But don’t rule out the trip to Mars yet, NASA states: “[NASA] does not currently have a limit for deep space missions, and is working with the National Academies Institute of Medicine to determine appropriate limits for deep space missions, such as a mission to Mars in the 2030s.”

Besides, other entities are thinking about going, such as Mars One.

Read more about the radiation findings in this Dec. 9 article on Science. The research was led by Don Hassler, a Southwest Research Institute program director and principal investigator of Curiosity’s radiation assessment detector (RAD).

Source: Southwest Research Institute

Posted on by Elizabeth Howell

Speedy Particles Whip At Nearly The Speed Of Light In Earth’s Radiation Belts

Artist's conception of NASA’s Van Allen Probes twin spacecraft. Credit: Andy Kale, University of Alberta

The radiation-heavy Van Allen Belts around Earth contain particles that can move at almost the speed of light across vast distances, new research reveals. The information came from an instrument flown aboard the Van Allen Probes twin NASA spacecraft, which launched in 2012.

According to scientists, the process that creates this is similar to what happens in the Large Hadron Collider and other particle accelerators. The magnetic field on the Earth accelerates electrons faster as these particles orbit the planet. While scientists had spotted this process happening at small scales before, the new paper has seen this across hundreds of thousands of kilometers or miles.

“With the Van Allen Probes, I like to think there’s no place for these particles to hide because each spacecraft is spinning and ‘glimpses’ the entire sky with its detector ‘eyes’, so we’re essentially getting a 360-degree view in terms of direction, position, energy, and time,” stated Harlan Spence, principal scientist for the Energetic Particle, Composition, and Thermal Plasma (ECT) instrument aboard the probes, and co-author on the research paper. He is also director of the University of New Hampshire Institute for the Study of Earth, Oceans, and Space.

The research was led by University of Alberta physicist Ian Mann, and is available in Nature Communications. “People have considered that this acceleration process might be present but we haven’t been able to see it clearly until the Van Allen Probes,” Mann stated.

Source: University of New Hampshire

Posted on by Fraser Cain

What is a Pulsar?

What is a Pulsar?

They are what is known as the “lighthouses” of the universe – rotating neutron stars that emit a focused beam of electromagnetic radiation that is only visible if you’re standing in it’s path. Known as pulsars, these stellar relics get their name because of the way their emissions appear to be “pulsating” out into space.

Not only are these ancient stellar objects very fascinating and awesome to behold, they are very useful to astronomers as well. This is due to the fact that they have regular rotational periods, which produces a very precise internal in its pulses – ranging from milliseconds to seconds.

Description:

Pulsars are types of neutron stars; the dead relics of massive stars. What sets pulsars apart from regular neutron stars is that they’re highly magnetized, and rotating at enormous speeds. Astronomers detect them by the radio pulses they emit at regular intervals.

An artist’s impression of an accreting X-ray millisecond pulsar. The flowing material from the companion star forms a disk around the neutron star which is truncated at the edge of the pulsar magnetosphere. Credit: NASA / Goddard Space Flight Center / Dana Berry

Formation:

The formation of a pulsar is very similar to the creation of a neutron star. When a massive star with 4 to 8 times the mass of our Sun dies, it detonates as a supernova. The outer layers are blasted off into space, and the inner core contracts down with its gravity. The gravitational pressure is so strong that it overcomes the bonds that keep atoms apart.

Electrons and protons are crushed together by gravity to form neutrons. The gravity on the surface of a neutron star is about 2 x 1011 the force of gravity on Earth. So, the most massive stars detonate as supernovae, and can explode or collapse into black holes. If they’re less massive, like our Sun, they blast away their outer layers and then slowly cool down as white dwarfs.

But for stars between 1.4 and 3.2 times the mass of the Sun, they may still become supernovae, but they just don’t have enough mass to make a black hole. These medium mass objects end their lives as neutron stars, and some of these can become pulsars or magnetars. When these stars collapse, they maintain their angular momentum.

But with a much smaller size, their rotational speed increases dramatically, spinning many times a second. This relatively tiny, super dense object, emits a powerful blast of radiation along its magnetic field lines, although this beam of radiation doesn’t necessarily line up with it’s axis of rotation. So, pulsars are simply rotating neutron stars.

And so, from here on Earth, when astronomers detect an intense beam of radio emissions several times a second, as it rotates around like a lighthouse beam – this is a pulsar.

History:

The first pulsar was discovered in 1967 by Jocelyn Bell Burnell and Antony Hewis, and it surprised the scientific community by the regular radio emissions it transmitted. They detected a mysterious radio emission coming from a fixed point in the sky that peaked every 1.33 seconds. These emissions were so regular that some astronomers thought it might be evidence of communications from an intelligent civilization.

Although Burnell and Hewis were certain it had a natural origin, they named it LGM-1, which stands for “little green men”, and subsequent discoveries have helped astronomers discover the true nature of these strange objects.

Astronomers theorized that they were rapidly rotating neutron stars, and this was further supported by the discovery of a pulsar with a very short period (33-millisecond) in the Crab nebula. There have been a total of 1600 found so far, and the fastest discovered emits 716 pulses a second.

Later on, pulsars were found in binary systems, which helped to confirm Einstein’s theory of general relativity. And in 1982, a pulsar was found with a rotation period of just 1.6 microseconds. In fact, the first extrasolar planets ever discovered were found orbiting a pulsar – of course, it wouldn’t be a very habitable place.

Interesting Facts:

When a pulsar first forms, it has the most energy and fastest rotational speed. As it releases electromagnetic power through its beams, it gradually slows down. Within 10 to 100 million years, it slows to the point that its beams shut off and the pulsar becomes quiet.

When they are active, they spin with such uncanny regularity that they’re used as timers by astronomers. In fact, it is said that certain types of pulsars rival atomic clocks in their accuracy in keeping time.

Pulsars also help us search for gravitational waves, probe the interstellar medium, and even find extrasolar planets in orbit. In fact, the first extrasolar planets were discovered around a pulsar in 1992, when astronomers Aleksander Wolszczan and Dale Frail announced the discovery of a multi-planet planetary system around PSR B1257+12 – a millisecond pulsar now known to have two extrasolar planets.

Artist's impression of the planets orbiting PSR B1257+12. Credit: NASA/JPL-Caltech/R. Hurt (SSC)
Artist’s impression of the planets orbiting PSR B1257+12. Credit: NASA/JPL-Caltech/R. Hurt (SSC)

It has even been proposed that spacecraft could use them as beacons to help navigate around the Solar System. On NASA’s Voyager spacecraft, there are maps that show the direction of the Sun to 14 pulsars in our region. If aliens wanted to find our home planet, they couldn’t ask for a more accurate map.

We have written many articles about stars here on Universe Today. Here’s an article about a newly discovered gamma ray pulsar, and here’s an article about how millisecond pulsars spin so fast.

If you’d like more information on stars, check out Hubblesite’s News Releases about Stars, and here’s the stars and galaxies homepage.

We have recorded several episodes of Astronomy Cast about stars. Here are two that you might find helpful: Episode 12: Where Do Baby Stars Come From, and Episode 13: Where Do Stars Go When they Die?

Posted on by Jason Major

Navy Researchers Put Dark Lightning to the SWORD

Dark lightning occurs within thunderstorms and flings gamma rays and antimatter into space. (Science@NASA video)

Discovered “by accident” by NASA’s Fermi Gamma-ray Space Telescope in 2010, dark lightning is a surprisingly powerful — yet invisible — by-product of thunderstorms in Earth’s atmosphere. Like regular lightning, dark lightning is the result of a natural process of charged particles within storm clouds trying to cancel out opposing charges. Unlike normal lightning, though, dark lightning is invisible to our eyes and doesn’t radiate heat or light — instead, it releases bursts of gamma radiation.

What’s more, these gamma-ray outbursts originate at relatively low altitudes well within the storm clouds themselves. This means that airplane pilots and passengers flying through thunderstorms may be getting exposed to gamma rays from dark lightning, which are energetic enough to pass through the hull of an aircraft… as well as anything or anyone inside it. To find out how such exposure to dark lightning could affect air travelers, the U.S. Naval Research Laboratory (NRL) is conducting computer modeling tests using their SoftWare for the Optimization of Radiation Detectors — SWORD, for short.

Terrestrial Gamma-ray Flashes (TGFs) are extremely intense, sub-millisecond bursts of gamma rays and particle beams of matter and anti-matter. First identified in 1994, they are associated with strong thunderstorms and lightning, although scientists do not fully understand the details of the relationship to lightning. The latest theoretical models of TGFs suggest that the particle accelerator that creates the gamma rays is located deep within the atmosphere, at altitudes between six and ten miles, inside thunderclouds and within reach of civilian and military aircraft.

These models also suggest that the particle beams are intense enough to distort and collapse the electric field within thunderstorms and may, therefore, play an important role in regulating the production of visible lightning. Unlike visible lightning, TGF beams are sufficiently broad — perhaps about half a mile wide at the top of the thunderstorm — that they do not create a hot plasma channel and optical flash; hence the name, “dark lightning.”

A team of NRL Space Science Division researchers, led by Dr. J. Eric Grove of the High Energy Space Environment (HESE) Branch, is studying the radiation environment in the vicinity of thunderstorms and dark lightning flashes. Using the Calorimeter built by NRL on NASA’s Fermi Gamma-ray Space Telescope they are measuring the energy content of dark lightning and, for the first time, using gamma rays to geolocate the flashes.

As a next step, Dr. Chul Gwon of the HESE Branch is using NRL’s SoftWare for the Optimization of Radiation Detectors (SWORD) to create the first-ever simulations of a dark lightning flash striking a Boeing 737. He can calculate the radiation dosage to the passengers and crew from these Monte Carlo simulations. Previous estimates have indicated it could be as high as the equivalent of hundreds of chest X-rays, depending on the intensity of the flash and the distance to the source.

Simulation of a Boeing 737 struck by dark lightning. Green tracks show the paths of gamma rays from the dark flash as they enter the aircraft from below. (Credit: U.S. Naval Research Laboratory)
Simulation of a Boeing 737 struck by dark lightning. Green tracks show the paths of gamma rays from the dark flash as they enter the aircraft from below.
(Credit: U.S. Naval Research Laboratory)

SWORD simulations allow researchers to study in detail the effects of variation in intensity, spectrum, and geometry of the flash. Dr. Grover’s team is now assembling detectors that will be flown on balloons and specialized aircraft into thunderstorms to measure the gamma ray flux in situ. The first balloon flights are scheduled to take place this summer.

Source: NRL News

Posted on by Jason Major

Plastic Protection Against Cosmic Rays?

The CRaTER instrument aboard NASA's Lunar Reconnaissance Orbiter measures the effect of cosmic rays on "human tissue-equivalent" plastic. (NASA)

It could work, say researchers from the University of New Hampshire and the Southwest Research Institute.

One of the inherent dangers of space travel and long-term exploration missions beyond Earth is the constant barrage of radiation, both from our own Sun and in the form of high-energy particles originating from outside the Solar System called cosmic rays. Extended exposure can result in cellular damage and increased risks of cancer at the very least, and in large doses could even result in death. If we want human astronauts to set up permanent outposts on the Moon, explore the dunes and canyons of Mars, or mine asteroids for their valuable resources, we will first need to develop adequate (and reasonably economical) protection from dangerous space radiation… or else such endeavors will be nothing more than glorified suicide missions.

While layers of rock, soil, or water could protect against cosmic rays, we haven’t yet developed the technology to hollow out asteroids for spaceships or build stone spacesuits (and sending large amounts of such heavy materials into space isn’t yet cost-effective.)  Luckily, there may be a much easier way to protect astronauts from cosmic rays — using lightweight plastics.

While aluminum has always been the primary material in spacecraft construction, it provides relatively little protection against high-energy cosmic rays and can add so much mass to spacecraft that they become cost-prohibitive to launch.

Using observations made by the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) orbiting the Moon aboard LRO, researchers from UNH and SwRI have found that plastics, adequately designed, can provide better protection than aluminum or other heavier materials.

“This is the first study using observations from space to confirm what has been thought for some time—that plastics and other lightweight materials are pound-for-pound more effective for shielding against cosmic radiation than aluminum,” said Cary Zeitlin of the SwRI Earth, Oceans, and Space Department at UNH. “Shielding can’t entirely solve the radiation exposure problem in deep space, but there are clear differences in effectiveness of different materials.”

Zeitlin is lead author of a paper published online in the American Geophysical Union journal Space Weather.

A block of tissue-equivalent plastic (Credit: UNH)
A block of tissue-equivalent plastic (TEP) Credit: UNH

The plastic-aluminum comparison was made in earlier ground-based tests using beams of heavy particles to simulate cosmic rays. “The shielding effectiveness of the plastic in space is very much in line with what we discovered from the beam experiments, so we’ve gained a lot of confidence in the conclusions we drew from that work,” says Zeitlin. “Anything with high hydrogen content, including water, would work well.”

The space-based results were a product of CRaTER’s ability to accurately gauge the radiation dose of cosmic rays after passing through a material known as “tissue-equivalent plastic,” which simulates human muscle tissue.

(It may not look like human tissue, but it collects energy from cosmic particles in much the same way.)

Prior to CRaTER and recent measurements by the Radiation Assessment Detector (RAD) on the Mars rover Curiosity, the effects of thick shielding on cosmic rays had only been simulated in computer models and in particle accelerators, with little observational data from deep space.

The CRaTER observations have validated the models and the ground-based measurements, meaning that lightweight shielding materials could safely be used for long missions — provided their structural properties can be made adequate to withstand the rigors of spaceflight.

Sources: EurekAlert and CRaTER@UNH

Posted on by Jason Major

New Study Shows Cosmic Rays Could Cause Alzheimer’s

Humans explore Mars in “Distant Shores,” an illustration by NASA artist Pat Rawlins

Cosmic rays from deep space could pose serious health risks to future astronauts on long-duration missions to Mars — even bringing on the memory-destroying symptoms of Alzheimer’s disease, according to the results of a new study from the University of Rochester Medical Center.

While NASA has its sights set on the human exploration of Mars within the next several decades, even with the best propulsion technology currently available such a mission would take about three years. Within that time, crew members would be constantly exposed to large amounts of radiation that we are protected from here by Earth’s magnetic field and atmosphere. Some of this radiation comes in the form of protons from the Sun and can be blocked by adequate spacecraft shielding materials, but a much bigger danger comes from heavy high-energy particles that are constantly whipping across the galaxy, shot out of the hearts of exploding giant stars.

“Because iron particles pack a bigger wallop it is extremely difficult from an engineering perspective to effectively shield against them. One would have to essentially wrap a spacecraft in a six-foot block of lead or concrete.” 

– M. Kerry O’Banion, M.D., Ph.D.

S047While health risks from these high-mass, high-charged (HZE) particles have long been known, the exact nature of the damages they can cause to human physiology is still being researched — even more so now that Mars and asteroid exploration is on NASA’s short list.

Now, a team from the University of Rochester Medical Center (URMC) in New York has announced the results of their research linking high-energy radiation — just like what would be encountered during a trip to Mars — to the degeneration of brain function, and possibly even the onset of Alzheimer’s disease.

“Galactic cosmic radiation poses a significant threat to future astronauts,” said M. Kerry O’Banion, M.D., Ph.D., a professor in the University of Rochester Medical Center (URMC) Department of Neurobiology and Anatomy and the senior author of the study. “The possibility that radiation exposure in space may give rise to health problems such as cancer has long been recognized. However, this study shows for the first time that exposure to radiation levels equivalent to a mission to Mars could produce cognitive problems and speed up changes in the brain that are associated with Alzheimer’s disease.”

In particular the team focused on iron ions, which are blasted into space by supernovae and are massive enough to punch through a spacecraft’s protective shielding.

“Because iron particles pack a bigger wallop it is extremely difficult from an engineering perspective to effectively shield against them,” O’Banion said. “One would have to essentially wrap a spacecraft in a six-foot block of lead or concrete.”

advances-in-treating-alzheimers-afBy exposing lab mice to increasing levels of radiation and measuring their cognitive ability the researchers were able to determine the neurologically destructive nature of high-energy particles, which caused the animals to more readily fail cognitive tasks. In addition the exposed mice developed accumulations of a protein plaque within their brains, beta amyloid, the spread of which is associated with Alzheimer’s disease in humans.

“These findings clearly suggest that exposure to radiation in space has the potential to accelerate the development of Alzheimer’s disease,” said O’Banion. “This is yet another factor that NASA, which is clearly concerned about the health risks to its astronauts, will need to take into account as it plans future missions.”

Read more: Space Travel is Bad For Your Eyes

While Mars explorers could potentially protect themselves from cosmic radiation by setting up bases in caves, empty lava tubes or beneath rocky ledges, which would offer the sort of physical shielding necessary to stop dangerous HZE particles, that would obviously present a new set of challenges to astronauts working in an already alien environment. And there’s always the trip there (and back again) during which time a crew would be very much exposed.

While this won’t — and shouldn’t — prevent a Mars mission from eventually taking place, it does add yet another element of danger that will need to be factored in and either dealt with from both health and engineering standpoints… or accepted as an unavoidable risk by all involved, including the public.

S044

How much risk will be considered acceptable for the human exploration of Mars — and beyond? (NASA/Pat Rawlings)

Read more on the URMC news page here, and see the full experiment report here.

Illustrations for NASA by Pat Rawlings. See more of Rawling’s artwork here. Inset image: comparison of human brains without and with Alzheimer’s. Source: WHYY.

 

Posted on by Ken Kremer

Can Humans Live on Mars?

Image caption: Curiosity is taking the first ever radiation measurements from the surface of another planet in order to determine if future human explorers can live on Mars – as she traverses the terrain of the Red Planet. Curiosity is looking back to her rover tracks and the foothills of Mount Sharp and the eroded rim of Gale Crater in the distant horizon on Sol 24 (Aug. 30, 2012). This panorama is featured on PBS NOVA ‘Ultimate Mars Challenge’ documentary which premiered on PBS TV on Nov. 14. RAD is located on the rover deck in this colorized mosaic stitched together from Navcam images by the image processing team of Ken Kremer & Marco Di Lorenzo. Credit: NASA / JPL-Caltech / Ken Kremer / Marco Di Lorenzo

Metallic robots constructed by ingenious humans can survive on Mars. But what about future human astronauts?

NASA’s plucky Mars Exploration Rover Opportunity has thrived for nearly a decade traversing the plains of Meridiani Planum despite the continuous bombardment of sterilizing cosmic and solar radiation from charged particles thanks to her radiation hardened innards.

How about humans? What fate awaits them on a bold and likely year’s long expedition to the endlessly extreme and drastically harsh environment on the surface of the radiation drenched Red Planet – if one ever gets off the ground here on Earth? How much shielding would people need?

Answering these questions is one of the key quests ahead for NASA’s SUV sized Curiosity Mars rover – now 100 Sols, or Martian days, into her 2 year long primary mission phase.

Preliminary data looks promising.

Curiosity survived the 8 month interplanetary journey and the unprecedented sky crane rocket powered descent maneuver to touch down safely inside Gale Crater beside the towering layered foothills of 3 mi. (5.5 km) high Mount Sharp on Aug. 6, 2012.

Now she is tasked with assessing whether Mars and Gale Crater ever offered a habitable environment for microbial life forms – past or present. Characterizing the naturally occurring radiation levels stemming from galactic cosmic rays and the sun will address the habitability question for both microbes and astronauts. Radiation can destroy near-surface organic molecules.

Researchers are using Curiosity’s state-of-the-art Radiation Assessment Detector (RAD) instrument to monitor high-energy radiation on a daily basis and help determine the potential for real life health risks posed to future human explorers on the Martian surface.

“The atmosphere provides a level of shielding, and so charged-particle radiation is less when the atmosphere is thicker,” said RAD Principal Investigator Don Hassler of the Southwest Research Institute in Boulder, Colo. See the data graphs herein.

“Absolutely, the astronauts can live in this environment. It’s not so different from what astronauts might experience on the International Space Station. The real question is if you add up the total contribution to the astronaut’s total dose on a Mars mission can you stay within your career limits as you accumulate those numbers. Over time we will get those numbers,” Hassler explained.

The initial RAD data from the first two months on the surface was revealed at a media briefing for reporters on Thursday, Nov. 15 and shows that radiation is somewhat lower on Mars surface compared to the space environment due to shielding from the thin Martian atmosphere.

Image caption: Longer-Term Radiation Variations at Gale Crater. This graphic shows the variation of radiation dose measured by the Radiation Assessment Detector on NASA’s Curiosity rover over about 50 sols, or Martian days, on Mars. (On Earth, Sol 10 was Sept. 15 and Sol 60 was Oct. 6, 2012.) The dose rate of charged particles was measured using silicon detectors and is shown in black. The total dose rate (from both charged particles and neutral particles) was measured using a plastic scintillator and is shown in red. Credit: NASA/JPL-Caltech/ SwRI

RAD hasn’t detected any large solar flares yet from the surface. “That will be very important,” said Hassler.

“If there was a massive solar flare that could have an acute effect which could cause vomiting and potentially jeopardize the mission of a spacesuited astronaut.”

“Overall, Mars’ atmosphere reduces the radiation dose compared to what we saw during the cruise to Mars by a factor of about two.”

RAD was operating and already taking radiation measurements during the spacecraft’s interplanetary cruise to compare with the new data points now being collected on the floor of Gale Crater.

Mars atmospheric pressure is a bit less than 1% of Earth’s. It varies somewhat in relation to atmospheric cycles dependent on temperature and the freeze-thaw cycle of the polar ice caps and the resulting daily thermal tides.

“We see a daily variation in the radiation dose measured on the surface which is anti-correlated with the pressure of the atmosphere. Mars atmosphere is acting as a shield for the radiation. As the atmosphere gets thicker that provides more of a shield. Therefore we see a dip in the radiation dose by about 3 to 5%, every day,” said Hassler.

Image Caption: Curiosity Self Portrait with Mount Sharp at Rocknest ripple in Gale Crater. Curiosity used the Mars Hand Lens Imager (MAHLI) camera on the robotic arm to image herself and her target destination Mount Sharp in the background. Mountains in the background to the left are the northern wall of Gale Crater. This color panoramic mosaic was assembled from raw images snapped on Sol 85 (Nov. 1, 2012). Credit: NASA/JPL-Caltech/MSSS/Ken Kremer/Marco Di Lorenzo

There are also seasonal changes in radiation levels as Mars moves through space.

The RAD team is still refining the radiation data points.

“There’s calibrations and characterizations that we’re finalizing to get those numbers precise. We’re working on that. And we’re hoping to release that at the AGU [American Geophysical Union] meeting in December.”

Image caption: Daily Cycles of Radiation and Pressure at Gale Crater. This graphic shows the daily variations in Martian radiation and atmospheric pressure as measured by NASA’s Curiosity rover. As pressure increases, the total radiation dose decreases. When the atmosphere is thicker, it provides a better barrier with more effective shielding for radiation from outside of Mars. At each of the pressure maximums, the radiation level drops between 3 to 5 percent. The radiation level goes up at the end of the graph due to a longer-term trend that scientists are still studying. Credit: NASA/JPL-Caltech/SwRI

Radiation is a life limiting factor to habitability. RAD is the first science instrument to directly measure radiation from the surface of a planet other than Earth.

“Curiosity is finding that the radiation environment on Mars is sensitive to Mars weather and climate,” Hassler concluded.

Unlike Earth, Mars lost its magnetic field some 3.5 billion years ago – and therefore most of its shielding capability from harsh levels of energetic particle radiation from space.

Much more data will need to be collected by RAD before any final conclusions on living on Mars, and for how long and in which type habitats, can be drawn.

Learn more about Curiosity and NASA missions at my upcoming free public presentations:

And be sure to watch the excellent PBS NOVA Mars documentary – ‘Ultimate Mars Challenge’ – which also features Curiosity mosaics created by the imaging team of Ken Kremer & Marco Di Lorenzo.

Ken Kremer

…..

Dec 6: Free Public lecture titled “Atlantis, The Premature End of America’s Shuttle Program and What’s Beyond for NASA” including Curiosity, Orion, SpaceX and more by Ken Kremer at Brookdale Community College/Monmouth Museum and STAR Astronomy club in Lincroft, NJ at 8 PM

Dec 11: Free Public lecture titled “Curiosity and the Search for Life on Mars (in 3 D)” and more by Ken Kremer at Princeton University and the Amateur Astronomers Association of Princeton (AAAP) in Princeton, NJ at 8 PM.

Posted on by Jason Major

NASA Probes Play the Music of Earth’s Magnetosphere

Launched on August 30, 2012, NASA’s twin Radiation Belt Storm Probe (RBSP) satellites have captured recordings of audible-range radio waves emitted by Earth’s magnetosphere. The stream of chirps and whistles heard in the video above consist of 5 separate occurrences captured on September 5 by RBSP’s Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrument.

The events are presented as a single continuous recording, assembled by the (EMFISIS) team at the University of Iowa and NASA’s Goddard Space Flight Center.

Called a “chorus”, this phenomenon has been known for quite some time.

“People have known about chorus for decades,” says EMFISIS principal investigator Craig Kletzing of the University of Iowa. “Radio receivers are used to pick it up, and it sounds a lot like birds chirping. It was often more easily picked up in the mornings, which along with the chirping sound is why it’s sometimes referred to as ‘dawn chorus.’”

The radio waves, which are at frequencies that are audible to the human ear, are emitted by energetic particles within Earth’s magnetosphere, which in turn affects (and is affected by) the radiation belts.

The RBSP mission placed a pair of identical satellites into eccentric orbits that will take them from as low as 375 miles (603 km) to as far out as 20,000 miles (32,186 km). During their orbits the satellites will pass through both the stable inner and more variable outer Van Allen belts, one trailing the other. Along the way they’ll investigate the many particles that make up the belts and identify what sort of activity occurs in isolated locations — as well as across larger areas.

Read: New Satellites Will Tighten Knowledge of Earth’s Radiation Belts

Audio Credit: University of Iowa. Visualisation Credit: NASA/Goddard Space Flight Center. (H/T to Peter Sinclair at climatecrocks.com.)

Posted on by Jason Major

New Satellites Will Tighten Knowledge of Earth’s Radiation Belts


Surrounding our planet like vast invisible donuts (the ones with the hole, not the jelly-filled kind) are the Van Allen radiation belts, regions where various charged subatomic particles get trapped by Earth’s magnetic fields, forming rings of plasma. We know that the particles that make up this plasma can have nasty effects on spacecraft electronics as well as human physiology, but there’s a lot that isn’t known about the belts. Two new satellites scheduled to launch on August 23 August 24 will help change that.

“Particles from the radiation belts can penetrate into spacecraft and disrupt electronics, short circuits or upset memory on computers. The particles are also dangerous to astronauts traveling through the region. We need models to help predict hazardous events in the belts and right now we are aren’t very good at that. RBSP will help solve that problem.”
– David Sibeck, RBSP project scientist, Goddard Space Flight Center

NASA’s Radiation Belt Storm Probes (RBSP) mission will put a pair of identical satellites into eccentric orbits that take them from as low as 375 miles (603 km) to as far out as 20,000 miles (32,186 km). During their orbits the satellites will pass through both the stable inner and more variable outer Van Allen belts, one trailing the other. Along the way they’ll investigate the many particles that make up the belts and identify what sort of activity occurs in isolated locations and across larger areas.

“Definitely the biggest challenge that we face is the radiation environment that the probes are going to be flying through,” said Mission Systems Engineer Jim Stratton at APL. “Most spacecraft try to avoid the radiation belts — and we’re going to be flying right through the heart of them.”

Read: The Van Allen Belts and the Great Electron Escape

Each 8-sided RBSP satellite is approximately 6 feet (1.8 meters) across and weighs 1,475 pounds (669 kg).

The goal is to find out where the particles in the belts originate from — do they come from the solar wind? Or Earth’s own ionosphere? — as well as to find out what powers the belts’ variations in size and gives the particles their extreme speed and energy. Increased knowledge about Earth’s radiation belts will also help in the understanding of the plasma environment that pervades the entire Universe.

Read: What Are The Radiation Belts?

Ultimately the information gathered by the RBSP mission will help in the design of future science and communications satellites as well as safer spacecraft for human explorers.

The satellites are slated to launch aboard a United Launch Alliance Atlas V rocket from Cape Canaveral Air Force Station no earlier than 4:08 a.m. EDT on August 24.

Find out more about the RBSP mission here.

Video/rendering: NASA/GSFC.

Posted on by Amy Shira Teitel

New Data Find a Silver Lining of Cosmic Radiation

Artist's illustration of the Lunar Reconnaissance Orbiter. CRaTER is the instrument center-mounted at the bottom of LRO. Credit: Chris Meaney/NASA.

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Cosmic radiation, it seems, may be a blessing and a curse. A team of scientists based at the University of New Hampshire have used data from the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on NASA’s Lunar Reconnaissance Orbiter (LRO) to measure radiation on the Moon’s surface. They’ve found that while radiation is fatal, it can also cause the chemical changes that form the foundations of biological structures. 

CRaTER was designed to measure and characterize radiation on the Moon. It uses plastic and silicon detectors that mimic human flesh to give scientists an idea of how damaging the environment is to humans; the radiation in this case is from both galactic cosmic rays and solar energetic particles. Both these types of radiation pose a known threat to astronauts and robotic spacecraft alike.

An illustration showing the natural barrier Earth gives us against solar radiation. Credit: NASA.

NASA’s LRO has managed to gather remarkably good data. Its recent measurements were made during a quiet solar period. The lower power, pressure, fluctuations, and magnetic fluctuations of the solar wind means less interruptions. The galactic cosmic rays and solar energy particles have been able to interact more readily with detectors. Since the instruments orbit the Moon, there isn’t even an atmosphere present to shield the blow of these rays and particles.

This is a unique occurrence that has given scientists with sufficient data to validate their models of cosmic radiation. “Now we can… project GCR dose rates from the present period back through time when different interplanetary conditions prevailed,” says Nathan Schwadron, associate professor of physics at the UNH Space Science Center within the Institute for the Study of Earth, Oceans, and Space. These types of projections provide a clearer picture of the effects of cosmic rays on airless bodies throughout the Solar System’s history.

These new, more accurate models can also effectively predict radiation hazards spawned by cosmic rays and solar particles. Schwadron says that these “validated models will be able to answer the question of how hazardous the space environment is and could be during these high-energy radiation events.” Being able to anticipate high radiation events and environments will be necessary for any manned space exploration planned to go beyond low-Earth orbit.

A bootprint on the lunar regolith. Credit: NASA.

But CRaTER’s most recent finding revealed something else interesting: cosmic radiation has another important effect on the bodies it hits. While fatal to humans and damaging to robots, cosmic radiation irradiates water and ice to cause chemical alterations. The process releases oxygen atoms from water ice, which are then free to bind with carbon to form large molecules that are “prebiotic” organic molecules. The radiation process also causes the lunar soil, regolith, to darken over time. This is important in understanding the geologic history of the moon.

The data recorded on radiation environments support the current models of Earth-Moon-Mars interplanetary space. The full paper, titled “Lunar Radiation Environment and Space Weathering from the Cosmic Ray Telescope for the Effects of Radiation (CRaTER),” was written by Schwadron and the director of EOS and lead scientist for the CRaTER instrument Harlan Spence and is published online in the American Geophysical Union’s Journal of Geophysical Research.

Source: University of New Hampshire