Yeast and people have a lot in common. About 1/3rd of our DNA is the same. Indeed, the DNA of yeast is so similar to that of humans, yeast can actually live with human genes spliced into their genetic code. This is why Spaceweather.com and the students of Earth to Sky Calculus have been flying yeast to the edge of space. Understanding how the microbes respond to cosmic rays could tell us how human cells respond as well. Here are three strains of yeast (one per test tube) flying 113,936 feet above Earth’s surface on August 15th:

The student in the picture is Joey, a high school senior, hitching a ride to the stratosphere along with the yeast. Joey and other members of the student research team are busy measuring growth curves and mutation rates for the space-traveling yeast.

One result is already clear: Yeast are incredibly tough. En route to the stratosphere they were frozen solid at temperatures as low as -63C, and they experienced dose rates of ionizing radiation 100x Earth normal. Survival rates in some of the returning samples were close to 100%.

Photo-micrographs show that yeast mutates in the stratosphere. This image, for instance, shows a colony of white mutants alongside the normal red colonies of Saccharomyces cerevisiae (HA2):

In addition to the white mutation shown above, the students have also observed petite mutants, which are a sign of changes in the cells’ mitochondrial genome. These changes are of interest to space biologists because the DNA repair mechanisms of yeast are remarkably similar to those of human beings. In particular, proteins encoded by yeast RAD genes are closely related to proteins used by human cells to undo radiation damage.

On the evening of Sept. 27th, Spaceweather.com and the students of Earth to Sky Calculus conducted a routine flight of their cosmic ray payload to the stratosphere. Routine, that is, except for one thing: the balloon flew at night during a lunar eclipse. One of the goals of the flight was to compare radiation levels at night to those recorded during the day. Here are the data they recorded:

Compare this plot of radiation vs. altitude to a similar plot recorded in broad daylight only a few days earlier. They are almost identical. Radiation levels in the stratosphere matched at the 1% level. Radiation levels at aviation altitudes (where planes fly) agreed within about 3%. Night and day were the same.

This simple experiment highlights something that is already well known to researchers. Cosmic rays in Earth’s atmosphere come mainly from deep space. They are accelerated toward Earth by supernovas, colliding neutron stars, and other violent events in the Milky Way. Flying at night is no safeguard against these energetic particles because they are ever-present, coming at us from all directions, day and night.

HEY THANKS (and Happy Birthday): The lunar eclipse flight was sponsored by Spaceweather.com reader JR Biggs, whose donation of $500 paid for the supplies neccesary to get the balloon off the ground. To say “thank you” for his contribution, we flew a birthday card for his daughter to the edge of space:

Happy Birthday to Autumn! She enjoyed watching a complete video of the flight when she turned 4 on Oct. 10th.

Readers, if you would like to support a research flight and send your birthday card, business logo, or other photo along for the ride, it only costs $500. Contact Dr. Tony Phillips to make arrangements.

by Dr. Tony Phillips (This article originally appeared on Spaceweather.com)

Spoiler alert: Stop reading now if you haven’t yet seen The Martian.

The #1 movie in theaters right now is The Martian, a film adaptation of Andy Weir’s eponymous book. It tells the heart-pounding story of fictional astronaut Mark Watney, who is stranded on Mars and ultimately rescued by the crewmates who had inadvertently left him behind. To survive long enough to be rescued, Watney has to “science the hell out of” a very tricky situation: he grows food in alien soil, extracts water from rocket fuel, dodges Martian dust storms, and sends signals to NASA using an old Mars rover that had been buried in red sand for some 30 years.

It’s a thrilling adventure told with considerable accuracy—except, perhaps, for one thing. “While Andy Weir does a good job of representing the risks faced by Mark Watney stranded on Mars, he is silent on the threat of radiation, not just to Mark but particularly to the crew of the Hermes as they execute a daring rescue mission that more than doubles their time in deep space,” says Dr. Ron Turner, Distinguished Analyst at ANSER, a public-service research institute in Virginia.

Space radiation comes from two main sources: solar storms and galactic cosmic rays. Solar storms are intense, short-lived, and infrequent. Fortunately for Mark, there weren’t any during his mission. He dodged that bullet. However, he and his crewmates could not have avoided cosmic rays. These are high-energy particles that arise from supernovas, colliding neutron stars, and other violent events happening all the time in the Milky Way. They are ever-present, 24/7, and there is no way to avoid them. So far, NASA has developed no effective shield against these sub-atomic cannon balls from deep space. “Doubling a nominal spacecraft shielding thickness only reduces the GCR [galactic cosmic rays] exposure by a few percent,” notes Turner.

In the movie, Watney is actually safer than the crew of the Hermes. Turner explains: “The radiation exposure is significantly less on the surface of Mars. For one thing, the planet beneath your feet reduces your exposure by half. The atmosphere, while thin, further reduces the dose. The dose rate on Mars, while high, is only about 1/3rd of that on the Hermes.”

The biggest threat from cosmic radiation exposure is the possibility of dying from radiation-induced cancer sometime after a safe return to Earth. NASA’s radiation limits today are set to limit this life-shortening risk to less than three percent. Taking into account many factors, such as the phase of the solar cycle and the number of days the crew spent in deep space and on the surface of Mars, Turner has calculated the total dose of cosmic rays absorbed by Watney (41 cSv) and the crew (72 cSv). “cSV” is a centi-Seivert, a unit of radiation commonly used in discussion of human dose rates.

There is considerable uncertainty in how these doses translate into an increased risk of cancer. Turner estimates the added risk to Watney as somewhere between 0.25% and 3.25%. For members of the crew, the added risk ranges from 0.48% to 7.6%. The high end of these ranges are well outside NASA safety limits. The crew especially could be facing medical problems after their homecoming.

Post-flight cancer is not the only problem, however. “There is some additional concern that sustained radiation exposure could lead to other problems that manifest during the mission, instead of years afterward. Possible examples include heart disease, reduced immune system effectiveness, and neurological effects mimicking the symptoms of Alzheimer disease.”

As far as we can tell, none of these things happened to the crew of the Hermes. It’s just as well. They had enough trouble without cosmic rays. For the complete details of Turner’s analysis CLICK HERE (pdf).

by Dr. Tony Phillips (This article originally appeared on Spaceweather.com)

05 Nov. 2015: Spaceweather.com and the students of Earth to Sky Calculus regularly fly helium balloons to the stratosphere to measure cosmic rays. For the past six months, May through Oct. 2015, they have been taking their radiation sensors onboard commercial airplanes, too. The chart below summarizes their measurements on 18 different airplanes flying back and forth across the continental United States.

The points on the graph indicate the dose rate of cosmic rays inside the airplanes compared to sea level. For instance, the dose rate for flights that cruised at 40,000+ feet was more than 50 times higher than the dose rate on the ground below. No wonder the International Commission on Radiological Protection (ICRP) classifies pilots as occupational radiation workers.

Cosmic rays come from deep space. They are high energy particles accelerated toward Earth by distant explosions such as supernovas and colliding neutron stars. Astronauts aren’t the only ones who have to think about them; flyers do, too. Cosmic rays penetrate deep inside Earth’s atmosphere where airplanes travel every day.

Our radiation sensors detect X-rays and gamma-rays in the energy range 10 keV to 20 MeV. These energies span the range of medical X-ray machines and airport security scanners.

Cosmic Rays are modulated by solar activity. Solar storms and CMEs tend to sweep aside cosmic rays, making it more difficult for cosmic rays to reach Earth. Low solar activity, on the other hand, allows an extra dose of cosmic rays to reach our planet. This is important because forecasters expect solar activity to drop sharply in the years ahead as we approach a new Solar Minimum. Cosmic rays are poised to increase accordingly.

The plot, above, tells us what is “normal” in 2015. How will it change as the solar cycle wanes? Stay tuned for regular updates.

by Dr. Tony Phillips (this article originally appeared on Spaceweather.com)

Approximately once a week, Spaceweather.com and the students of Earth to Sky Calculus fly “space weather balloons” to the stratosphere over California. These balloons are equipped with radiation sensors that detect cosmic rays, a surprisingly “down to Earth” form of space weather. Cosmic rays can seed clouds, trigger lightning, and penetrate commercial airplanes. Our measurements show that someone flying back and forth across the continental USA, just once, can absorb as much ionizing radiation as 2 to 5 dental X-rays. Here is the data from our latest flight, Oct. 11th:

Radiation levels peak at the entrance to the stratosphere in a broad region called the “Pfotzer Maximum.” This peak is named after physicist George Pfotzer who discovered it using balloons and Geiger tubes in the 1930s. Radiation levels there are more than 80x sea level.

Note that the bottom of the Pfotzer Maximim is near 55,000 ft. This means that some high-flying aircraft are not far from the zone of maximum radiation. Indeed, according to the Oct 11th measurements, a plane flying at 45,000 feet is exposed to 2.77 uSv/hr. At that rate, a passenger would absorb about one dental X-ray’s worth of radiation in about 5 hours.

The radiation sensors onboard our helium balloons detect X-rays and gamma-rays in the energy range 10 keV to 20 MeV. These energies span the range of medical X-ray machines and airport security scanners.

Oct. 11, 2015, Balloon Flight Photo Gallery

Hey thanks! The cosmic ray research described above is 100% crowd-funded. Our Oct. 11th balloon flight was made possible by a generous donation of $500 from Spaceweather.com reader Vicki Brown. To say thanks, we flew Vicki’s parents, Betty and Earl, to the edge of space:

“I am so happy to help the young scientists, and it is cool to see my folks in the stratosphere!” says Vicki.

Readers, have you ever wanted to send a loved one to the stratosphere? You can make it happen by sponsoring a cosmic ray research flight. Contact Dr. Tony Phillips for details.

by Dr. Tony Phillips

27 Sept. 2015: Once a week, and sometimes more often, Spaceweather.com and the students of Earth to Sky Calculus fly “space weather balloons” to the stratosphere. These balloons are equipped with radiation sensors that detect cosmic rays, a form of space weather important to people on Earth. Cosmic rays can alter the chemistry of the upper atmosphere, seed clouds, spark exotic forms of lightning, and penetrate commercial airplanes. This last point is of special interest to the traveling public. Our measurements show that someone flying back and forth across the continental USA, just once, can absorb as much ionizing radiation as 2 to 5 dental X-rays.

Here is an example of our data from a typical balloon flight:

This radiation profile was obtained on the evening of Sept. 27, 2015–incidentally, during a total eclipse of the Moon.  The altitude of the balloon is on the horizontal axis, radiation dose rates are on the vertical axis. Inset photos show scenes from the mission.

Radiation levels peak at the entrance to the stratosphere in a broad region called the “Pfotzer Maximum.” This peak is named after physicist George Pfotzer who discovered it using balloons and Geiger tubes in the 1930s. Radiation levels there are nearly 100x sea level.

Note that the bottom of the Pfotzer Maximim is near 55,000 ft. This means that some high-flying aircraft are not far from the zone of maximum radiation. Indeed, according to the Sept. 27th measurements, a plane flying at 45,000 feet is exposed to 288 uRads/hr. At that rate, a passenger would absorb about one dental X-ray’s worth of radiation in 5 hours.

The radiation sensors onboard our helium balloons detect X-rays and gamma-rays in the energy range 10 keV to 20 MeV. These energies span the range of medical X-ray machines and airport security scanners.

by Dr. Tony Phillips (Spaceweather.com)

July 30, 2015 — Many people think that only astronauts have to worry about cosmic radiation. Not so. Regular air travelers are exposed to cosmic rays, too. This week, Spaceweather.com’s Dr. Tony Phillips and the students of Earth to Sky Calculus flew across the United States to conduct a transcontinental launch of space weather balloons. They took radiation sensors on board the plane to find out how many cosmic rays they would absorb during the flight. Here are the data they collected flying east:

Radiation levels in the cabin of the Airbus 319 (Spirit Airlines flight 640) tripled within ten minutes after takeoff, and were nearly 30 times ground level by the time the plane reached cruising altitude at 39,300 feet. Summing over the entire flight, the sensors measured about 1 mrem of radiation–similar to a dental x-ray.

There was no solar storm in progress. The extra radiation was just a regular drizzle of cosmic rays reaching down to aviation altitudes. This radiation is ever-present and comes from supernovas, black holes, and other sources across the galaxy.

The Earth to Sky team consisted of five people who sat in three different locations: First Class, over the wings, and in the back row. Would they all absorb the same dose? No. On this particular flight, dose rates were highest in First Class and lowest near the toilets in the rear. The front-to-back ratio was as high as 13%. This gradient is not understood; presumably, it has to do with the way cosmic rays interact with the plane’s fuselage and fuel tanks.

Five days later, following a successful Transcontinental Balloon Launch, the team flew back to the west coast. Once again they flew on an Airbus 319 (Spirit Airlines flight 641), non-stop from Boston to Las Vegas. The results were similar:

As before, the First Class seats registered the highest dose of radiation–as much as 6% higher than the wings and rear of the plane. On this flight we added a second radiation sensor to First Class to confirm the effect. Both sensors agreed: ionizing radiation was slightly higher in the front of the plane.

Because cosmic rays come from space, radiation inside the airplane grows stronger as the airplane ascends. This plot shows how the dose rate changed as a function of altitude throughout the July 23rd flight:

Note how radiation levels remain low at altitudes below ~15,000 ft. Earth’s atmosphere does a good job shielding those altitudes from cosmic rays. Above 15,000 ft, however, dose rates climb rapidly as the plane ascends.

The radiation sensors are the same ones that Earth to Sky Calculus routinely flies onboard helium balloons to measure cosmic rays in the stratosphere. They detect X-rays and gamma-rays in the energy range 10 keV to 20 MeV. These energies span the range of medical X-ray machines and airport security scanners.