When NASA’s Artemis 1 lifts off Monday from a Florida launch pad, it will take no human crew on a 42-day mission to orbit the moon and return to Earth. But experiments aboard the rocket could solve a thorny problem that stands in the way of long-duration human spaceflight: cosmic radiation.
University of British Columbia pharmaceutical scientist Corey Nislow was just a toddler when Apollo 11 landed on the moon in 1969. The human crew spent less than a day on the lunar surface beyond the protection against cosmic radiation provided by the Earth’s magnetic field, which deflects it towards the Van Allen belts around the planet.
Apollo 17, the last human journey to the moon completed fifty years ago in December, lasted just 12 days.
“Once you leave the safety of the Van Allen belts,” Nislow said, “there is currently no shielding available that can protect biological material, including crew members, from the effects of cosmic radiation. “
These effects can include everything from an increased risk of developing cataracts to cancer. The International Space Station (ISS) is in Low Earth Orbit (LEO) and astronauts aboard the ISS are inside Earth’s protective magnetosphere.
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But extended missions to the Moon and what NASA expects will be a nearly two-year return trip to Mars pose serious risks.
“Frankly, if we go to Mars, a round trip will expose a crew member to between 10 and 100 times the radiation limit,” Nislow said.
1st biological material beyond Earth orbit in 50 years
The work Nislow and his collaborators are doing with NASA to mitigate the effects of cosmic radiation will send the first biological material beyond Earth’s orbit in 50 years. And the replacement for living astronauts is something most people have in their pantry: yeast.
“Even though yeast and human beings are separated by a million years of evolution, half of all yeast genes function almost the same as human genes,” Nislow said.
Yeast, a single-celled microorganism, has about 6,000 genes. Nislow, Tier 1 Canada Research Chair in Translational Genomics, says yeast cells from the experiment aboard the Orion spacecraft atop Artemis 1 were individually modified to produce 6,000 genetically unique versions . Each version has a different gene removed and replaced with a unique short DNA splice known as a barcode, allowing researchers to easily identify and track the variant.
Once the spacecraft is beyond the protection of Earth’s magnetic field, the dried yeast will be remotely rehydrated so it can grow and divide while being bombarded with cosmic radiation. Five or six weeks later, when the spacecraft runs aground in the Pacific Ocean, the shoebox-sized container containing the experiment will be recovered and returned to Nislow’s lab at UBC. The hope is to find individual genes in the cells that resisted the radiation or were able to repair the damage.
“And then we can ask what drugs or chemicals at our disposal might help reduce the susceptibility of a particular gene and that’s where we go to countermeasures,” Nislow said.
Yeast cells make perfect astronauts
It’s a fascinating opportunity, according to Professor Doug Boreham, a radiation biologist at the Northern Ontario School of Medicine in Sudbury.
“They’re going to be looking at survival when they get these things back, which is very cool,” Boreham said, noting that yeast cells make perfect astronauts. “They don’t need to breathe. They don’t need water. They don’t eat. They don’t care about the temperature. But yet they’re alive.”
In fact, yeast cells are such ideal substitutes for humans that they’re central to a different experience aboard Artemis that Boreham and his colleagues are helping to support. BioSentinel is a small satellite the size of a cinder block that will be deployed in deep space. It contains yeast samples that will be rehydrated in stages over a period of several weeks using a blue nutrient solution.
The solution turns pink as the yeast metabolizes and an onboard optical sensor will measure the color changes. Cells that cannot repair damage caused by cosmic radiation will be less pink and more blue. But the samples will not return to Earth for study. BioSentinel will transmit data in orbit around the Sun until it runs out of power.
Boreham is involved in the science project, which he says will involve comparing data from BioSentinel with that of samples grown simultaneously at his university and two kilometers underground at SNOLAB, Canada’s deep underground research facility.
“We’re looking at the fundamental mechanisms involved in cells managing and repairing the effects of cosmic radiation,” Boreham said, acknowledging that there are limits to the experiments.
Single-celled organisms like yeast just want to grow and divide, he says. Human cells, however, can “communicate” with each other. Human cells exposed to stress and damage like radiation create free radicals that boost our immune system. Humans also possess tumor suppressor genes, which can cause irreparable cells to self-destruct.
“You can’t get that in a yeast model,” Boreham said.
“Very important experiences”
But all of this is critical work, according to Canadian astronaut Dr Roberta Bondar.
“These are very, very important experiments and these are things that we need to do very soon,” Bondar said.
Bondar, who is a neurologist, flew aboard NASA’s space shuttle Discovery 30 years ago and then analyzed astronaut health data from two dozen missions. She says the effects of radiation on any long-duration spaceflight could wreak havoc on the mission.
“So that includes things like impaired cognitive function or maybe even impaired motor function and behavioral changes,” Bondar says. “These are things that would be scary in an enclosed environment in a certain type of spacecraft.”
Nislow believes that until a way to mitigate these radiation risks is found, it would be unethical to send humans on space travel lasting longer than a year.
And he hopes that experiments using one of the oldest life forms on the planet will allow humans to travel safely to other worlds.
“Without being hyperbolic, this is a very, very important step.”