The sun was quiet during all six Apollo missions that landed humans on the moon. Neither astronauts nor vessels were exposed to violent storms that throw off damaging solar energetic particles. It was an extraordinary piece of luck. But in August 1972, midway between the date the astronauts of Apollo 16 had returned home and when those of Apollo 17 took off on the final voyage, the sun spewed out the biggest storm it had produced in a century.
Earlier in his career, as Daniel Baker became more involved in NASA and in space weather, he began to wonder what would have happened if a solar storm had struck while astronauts were walking on the moon during that fabled Apollo era. The moon no longer has an internally generated magnetic field or an atmosphere to protect against radiation, leaving astronauts exposed apart from their space suits. He asked what the emergency plan had been. The answer? The astronauts were instructed to dig a hole, and then the more senior would lie down in the hole and the junior would lie on top of him, shielding his superior’s body with his own. The hope was that at least one astronaut would be undamaged enough to make it back to Earth. The August 1972 storm was so strong that any humans exposed to it would have suffered acute radiation sickness and would likely have died, Baker said. “It points out that without the protection of a magnetic field, we are very susceptible.”
Space, rather than being the calm, empty, and benign place our forebears envisioned, is full of lethal ionizing radiation. When the poles reverse and the Earth’s shield is weakened, some of that solar and galactic radiation will reach into the lower atmosphere and even parts of the surface, Baker said. If people and other species cannot escape to safer parts of the planet, they will suffer the effects of radiation, both debilitating and fatal, some of it akin to what the astronauts would have experienced had they been on the moon in August 1972. During a reversal, Baker expects to see more cancer affecting the eyes, mucous membranes, and stomach lining. He expects to see widespread, acute radiation poisoning of the type seen in the wake of radiation accidents and nuclear warfare. That means both immediate and chronic effects on human health. And while some geophysicists said it’s hard to tell how much increased radiation will accompany a reversal and that the fallout may not be as severe as Baker predicted, many said that a common estimate is for cancer rates to increase by 20 percent across the board. That “war on cancer” is looking a lot more challenging.
Scientists and physicians have studied the effects of radiation on living tissue since the short electromagnetic waves, dubbed X-rays—after the scientific unknown x—were discovered in 1895 by Wilhelm Röntgen, the Dutch/German physicist. He famously took an X-ray of the left hand of his wife, Anna, showing the startling, ghostly images of the bones within her hand, plus the outline of the wedding ring on her finger. He won the Nobel Prize in physics for the discovery in 1901. Reports of damage from exposure to the mysterious rays began almost immediately, including burns, hair loss, and death. One of the first deaths from cancer caused by X-ray exposure was Clarence Dally, a glassblower who worked with the American electricity magnate Thomas Edison in his efforts to make an X-ray focus tube. Being right-handed, Dally repeatedly tested the X-ray on his left hand. When it became too injured, he switched to his right. He died in 1904 at age thirty-nine, but not before his left arm had been amputated at the shoulder, and the right above the elbow in a failed bid to stop the galloping damage. Edison abandoned X-rays in horror.
A year after Röntgen discovered X-rays, the French physicist Henri Becquerel found evidence that uranium spontaneously ejects particles—this is the weak nuclear force at work—making what was soon called a “radioactive” substance. Radioactive materials are also ionizing. They are uncommon in nature. Immediately after Becquerel discovered uranium’s odd characteristics, Marie and Pierre Curie experimented with it and discovered the radioactive substances radium and polonium. Together, the three received the Nobel Prize in physics in 1903. As with X-rays, the injuries and deaths from working with spontaneously radioactive material began to mount quickly, although the dangers were not fully recognized for decades. At one time, radium cures were on offer to freshen one’s complexion or clear one’s bowels. Marie Curie, who carried tubes of radioactive material around in her lab-coat pockets, died in 1936 at age sixty-six from aplastic anemia, or damage to her bone marrow, likely from exposure to radiation. Her notes in the National Library of France in Paris are still encased in lead-lined boxes, a radioactive shield.
Today, most of the work estimating the risks of illness and death from radiation of any sort, whether from radioactive substances or ionizing electromagnetic radiation, comes from research on the survivors of the Hiroshima and Nagasaki atomic bombs dropped in 1945. There is also information about people who were exposed to radiation during nuclear accidents or whose nuclear medicine treatments went awry. When it comes to data on space travelers, the twenty-four Apollo astronauts are the only humans to have left lower-Earth orbit. In addition, there are records from astronauts who have orbited Earth on shuttles or resided on the International Space Station, all of which activity has taken place within the protection of the Van Allen belts. Any other information on damage from solar and galactic particles is experimental or theoretical.
At the most basic level, radioactive substances and radiation from electromagnetic waves and solar and cosmic energetic particles damage living beings in similar ways. Differences among them have to do with how much energy the particles or waves have, how big the particles are, and how close you are to them. Spontaneous radioactive decay, like the uranium, radium, and polonium the Curies worked with, involves a large, unwieldy atom with too many neutrons that is trying to become stable. A common way for an atom to do that is to throw off subatomic particles, tiny bits of itself. Sometimes a radioactive atom throws off a neutron or two in what’s called neutron release. Sometimes it’s two neutrons and two protons joined together, making a new helium nucleus with a positive charge. That’s called alpha decay. Sometimes it throws off an electron. That’s beta decay. Sometimes the protons and neutrons rearrange themselves, like people taking their seats for a concert after a cocktail party, and the atom emits electromagnetic energy in the form of gamma rays. The point for us is that charged particles or energetic neutrons or nuclei or tiny fast electromagnetic waves are being emitted that can cut through cells and damage them.
Take uranium as an example. It exists naturally on Earth in three isotopes. It always has 92 protons in the nucleus—because when the number of protons changes, so does the name of the element—but different numbers of neutrons, either 146, 143, or 142. You add the neutrons to the protons to name the isotope. The most common on Earth is uranium-238, which has 146 neutrons. It stabilizes itself by alpha decay, transforming into thorium-234, with 90 protons and 144 neutrons, shedding a helium nucleus (two protons, two neutrons) in the process. The isotopes created during radioactive decay are called daughters. Eventually, after many alchemical transformations, uranium-238 becomes lead-206—boring and stable.
Some radioactive isotopes lend themselves to fission, meaning you can bombard them with neutrons to prompt them to split into lighter isotopes that then spontaneously keep splitting and releasing energy in a chain reaction. Uranium-235, with 143 neutrons, is prone to chain reactions. Uranium-238 can be converted into plutonium-239, which chain reacts. The bomb that struck Hiroshima contained uranium-235; the one dropped on Nagasaki, plutonium-239. Scientists have also learned how to harness the power of these types of radioactive chain reactions in nuclear power reactors to produce electricity, often using uranium-235.
Here’s how it connects to a reversal. All living things are made from atoms bonded into molecules through their electrons. Ionizing radiation and radioactive emissions break the bonds, either damaging the cell directly or creating knock-on chemical changes in a cell that can lead to its damage or death. As they break the bonds, they free up electrons, setting them in motion and endowing them with enough energy to ionize and excite other molecules in the tissue along a track of damage known as a linear energy transfer, or LET. The strength of the energy transferred is measured in megaelectron volts, or MeVs, named after Alessandro Volta, who invented the voltaic pile. X-rays are low LET. Galactic cosmic rays are very high. The energy transfer can create highly unstable ions within a tissue. The ions want to gain stability, so they scavenge bits from other molecules, damaging tissue in the process. A prime spot for an unstable ion to grab something is from a strand of DNA. Medical articles on the damage from ionizing radiation often feature microscope photographs of DNA. The tracks left by the radiation resemble rips left by a jagged knife dragged through a ribbon.
Astronauts are considered radiation workers, just like people who work with nuclear reactors. Their main occupational hazard has been pegged to be the risk of cancer from radiation. Their cumulative exposure over time is carefully tracked, and they wear dosimeters to record radiation during their missions. But radiation is tricky. The damage from a long, slow exposure of a fixed amount would be different from a short, intense exposure of that same amount. Chronic health problems, leading potentially to cancer, are linked to the long, slow exposure. The prime space risk for slow exposure comes from galactic cosmic rays. Those rays, which are high-energy protons and nuclei thought to have been created by explosions of supernovas in the Milky Way, are thrust through space with so much force that some of them are unstoppable by any shield. They carry far more energy than even the most powerful solar particles. They may be even more apt to cause the biological injuries that lead to cancer than other types of radiation, for unknown reasons, NASA has said.
By contrast, the prime risk for catastrophic immediate injury, called acute radiation sickness, is from a large solar particle event. That involves quick, devastating exposure that overwhelms the body’s threshold for radiation. The 200,000 or so people who died in the atomic bombings in Japan in 1945 were killed by acute poisoning, and so was Alexander Litvinenko, a former Russian officer who died in London in 2006 after being slipped the radioactive polonium-210, possibly in a cup of tea. It took him three weeks to die. Images of him, hairless and nearly without eyelashes, lying sick in a hospital bed, flooded the media. Acute radiation sickness begins swiftly. Cells that reproduce quickly in the body, such as hair follicles, those lining the gut, and blood-making cells in bone marrow, are the first to be affected. Nausea comes. Then vomiting. Fatigue, anorexia, and fever follow, and then hemorrhage as bone marrow fails. Death follows if the bone marrow is badly damaged enough. A bone marrow transplant can occasionally save a life if the exposure was relatively low.
But while cancer is the most feared outcome and is perceived as the highest risk, exposure to high levels of radiation has been found to carry many other health effects. Impaired immunity leading to bacterial and viral illness, short-term memory loss, increased risk of heart attack, and blindness can happen soon after exposure. Over time, the risks are for cataracts, fetal malformations, and sterility. Radiation from galactic cosmic rays, particularly the heavy ions, has recently also been linked to damage to the central nervous system, part of the body that had previously been thought to be able to fend off injury. Now it appears that the radiation can prompt the central nervous system to age long before its time, fostering dementia, Alzheimer’s disease, Parkinson’s disease, and other forms of cognitive harm in the relatively young.
Driven not by a possible pole switch but by the push to send long-term missions to the unprotected planet of Mars in the 2030s, scientists are trying to collect more information about exactly how space radiation affects living tissue. At the moment, they don’t know whether it has precisely the same effects as terrestrial sources of radiation, such as X-rays, gamma rays, and radioactive substances. To test this, and see if they can invent effective shields, they have developed materials that resemble human flesh. Known as tissue-equivalent plastic, the most popular formulation has the appearance of a very stiff black crayon. In 2009, they sent some in a telescope to orbit the moon, carefully calibrated to resemble the thickness of muscle that space radiation would have to penetrate before it reached vulnerable bone marrow. Its job is to measure the amount of energy the particles would deposit in tissue and electronics. Results are still being analyzed.
In the meantime, other researchers sent a radiation detector to Mars along with NASA’s Curiosity rover, which was on a mission to determine whether the red planet could support any life. The monitor was shielded with the same material intended to protect astronauts who might travel to Mars. But bad news: During the 253 days it took to travel to Mars from Earth, from November 26, 2011, to August 6, 2012, the monitors, even shielded, absorbed so much radiation that enduring it would be tantamount to cutting twenty years off one’s life. A separate analysis of the radiation that astronauts would likely encounter on an extended trip to Mars found that a single intense solar energetic particle event could simply kill everyone. So far, there are no effective barriers.
Baker and I had talked for hours by this time, trying to imagine the world of the future.
(Might we have to live underground? I asked. Maybe, he said.) He mused about whether space-weather television channels would become a hot item over time. Quoting, he joked, either Niels Bohr or Yogi Berra, he cracked a rare smile and told me that it’s tough to make predictions, especially about the future.
Privately, I took things much further. As the field dwindles, will we become nomads, wandering the Earth with magnetometers to track parts of the planet that have retained remnants of the magnetic field? I wondered if the equinoxes, the two days a year when night and day are the same length, linked to geomagnetic disturbances, will become days of mass terror. Or whether religious sects will emerge to placate an angry sun god, a weird postmodern parallel to the citizens of ancient Egypt and Mexico who worshipped the sun for more benign reasons. Or perhaps necessity will force our magnetic sixth sense to reemerge, allowing us once again, like birds, to see the field in order to survive. I could envision the possibility of cancer communes springing up like the leper colonies of old. Or refuges for the radioactively poisoned or for teenagers whose brains the rays have pushed to early dementia. Will suits of stiff black crayon be all the rage?
And then there were psychological questions. I wondered what it will feel like if the lights, that ultimate symbol of civilization’s progress, go out. Or how we know where we are when we have four or eight poles. Or where we come from, once the current north pole moves to the south. How does a species so used to controlling the conditions of life adapt to the fact that this revolution within the core is happening no matter what we do?
I left Baker’s office overlooking the Rockies, deep in contemplation about the fate of life as we know it. One thing he had said near the beginning of our time together had fastened itself to my imagination. It was not a fact but an image, told with wonder.
He was talking about the solar dynamo and how, for a time, scientists were sure that they understood it fully. The last solar cycle proved them wrong when their predictions about its activity turned out to be wholly incorrect. That’s what he thinks about when he considers the state of knowledge of the Earth’s tortured magnetic field. It is weakening. The north pole is on the run. The South Atlantic Anomaly is shifting, gaining ground fast and becoming a stronger agent for change. All these indicate mysterious goings-on below the surface of this spinning magnet we live on. It’s as if they are pushing up against an opaque glass and, try as we might, we can make out only their shadowed forms.