After nearly 65 years of human spaceflight, we are still finding out just how dangerous it is for the human body to travel to space. Sure, we all know about the need for pressurized suits and breathable air for astronauts. We’ve read about a growing body (excuse the pun) of knowledge about how low-gravity environments and weightlessness affect astronauts. Specifically, there are effects on their hearts, eyes, and bones. And, of course, we know about the dangers of simply lifting off from the planet (or returning to it after a mission). All those are unforgettable challenges. They must be solved if humans are to spend long periods of time traveling to other planets or building space installations. But, did we ever think about what happens to our blood in space?

It turns out there’s one more danger to add to the list: the risk of developing space anemia. It turns out that traveling in space for long periods of time destroys red blood cells in an astronaut’s body. This space anemia isn’t a new problem—space medicos have known about it for a long time. What they needed to do was nail down the specifics of when the anemia started. That meant studying several astronauts from the time they arrived in space to the time they came home. That way, doctors could figure out what happened to the red blood cells at different times in a mission.

The leading researcher, Dr. Guy Trudel, who works at Ottawa Hospital and teaches at the University of Ottawa, put together a team that devised a series of techniques to find out how much being in space affected astronaut blood cells. They did this by measuring red blood cell destruction in 14 astronauts who each spent six months onboard the ISS.

Changes in Blood in Space

People generally tend to generate and destroy about two million red blood cells each second. This is entirely normal and part of the way we live here on Earth. In space, those numbers change quite a bit. It turns out that astronaut bodies destroy 54 percent more red blood cells during their time in space than they do here on Earth. That’s true for all astronauts and the same whether they are male or female.

Now, the high loss of blood cells didn’t affect the health of the astronauts, and the team assumed that the astronauts more than made up for the red blood cell loss by generating extra ones during their time in space. Still, several of the astronauts turned out to be clinically anemic when they landed back on terra firma. The good news is that anemia reversed itself over the course of three or four months after the astronauts were safely back on Earth. Interestingly, the team measured astronauts again one year after their missions and found that red blood cell destruction was still 30 percent above preflight levels. It turns out that structural changes may have happened to the astronaut while they were in space that changed red blood cell control for up to a year after long-duration space missions.

The Implications in Space and on Earth


This discovery has some interesting implications for future missions—as well as for anemia patients here on Earth. For space travelers, if anemia is going to be a constant threat, then agencies will need to take some action. Obviously, some pretty strict screening of astronauts or space tourists for existing blood or health conditions is necessary. Second, it turns out that the longer the space mission, the worse the anemia gets. That presents some pretty big challenges for long-duration missions to the Moon and Mars.

Those trips will not be quick jaunts—they could be months or years long. So, the threat of anemia could very well affect the mission. Third, this tendency toward increased red blood cell production will change the kinds of diets astronauts eat while on mission. Finally, it’s unclear how long a space traveler can maintain an accelerated rate of destruction and production of red blood cells.

On Earth, patients with blood disorders are often anemic after being very ill for a long time; and limited mobility during illness is a factor. To get even more specific, anemia hinders a person’s ability to exercise and recover. Bedrest has been shown to cause anemia, but how it does this is unknown. However, the mechanism behind this Earth-based effect on red blood cells may be quite similar to the one that causes space anemia. If that’s true, blood doctors may have a new avenue of study to figure out what’s causing a person’s anemia. If the mechanism is the same on both Earth and in space, that’s a breakthrough. It means they can figure out ways to treat it—and maybe even prevent it.

If you want to know more about the study, there’s a paper published in the journal Nature Medicine that gives details.

Every once in a while, it’s a good idea to appreciate our somewhat-lucky place in the galaxy. How lucky? Well, it turns out the Sun and solar system move through space encased in a bubble. That “Local Bubble” is about a thousand light-years across, and the Sun happens to be sitting right in the middle. That gives astronomers a good vantage point in all directions.

A story last week about the Local Bubble caught my attention. That’s because we—and the bubble—are moving through a larger area of the galaxy called the “Local Interstellar Cloud”. It’s also known as the “Local Fluff”. This is a region where the density of hydrogen is a bit higher than the rest of nearby space. Some have suggested it’s more like a “void” compared to Earth’s upper atmosphere, for example, but it’s still a distinct structure with its own temperature and densities.

The Sun has been transiting this “Fluff” for about 10,000 years and may be about to leave it. There’s been a lot of scientific speculation about what things will be like when we do finish moving through it, in maybe a couple of thousand years. Will we be subject to higher rates of cosmic rays? What else? Good questions for which there are incomplete answers.

Astronomers have known about the Fluff and the Bubble for some decades now. Until recently, they didn’t have enough data to completely understand their nature. Some years ago, Hubble Space Telescope was used to study the Fluff and characterize its size and density. Astronomers have also used measurements made by the Voyager spacecraft to help probe this region of space. More recently, the Gaia spacecraft has been used to give astronomers a 3D look at the immediate neighborhood around the Sun.

Starbirth to Stardeath

The Bubble is a fascinating part of the local galactic structure. Think of it as a cavity in the interstellar medium. That cavity is a low-density, high-temperature plasma held in place by an outer “shell” of cold, neutral gas. It began forming about 14 million years ago thanks to a burst of starbirth activities. Among those newborn stars were massive ones with short lives. They died in supernova outbursts that pushed hot gases and other elements out into the surrounding interstellar medium. That created the cold gas shell which now forms the outer boundary of the bubble. So, think of it like blowing hot air into a balloon, and then watching the expansion the balloon makes into the colder outside air.

Interestingly enough, nearly all the active molecular clouds where starbirth is taking place closest to the solar system are located on the surface of the expanding bubble. The ongoing expansion of the bubble pushed those clouds together. That caused them to condense and collapse, which begin the process of star formation.

Finding the Bubble’s Characteristics

To understand the bubble and related star formation action, astronomers used data from the Gaia mission. It’s is mapping the Milky Way, giving a “3D view” of the stars in the galaxy. This helped them figure out the dimensions of the Local Bubble and the regions of starbirth on its surface. It’s providing an interesting look at the mechanics of supernova-driven star formation in our local neighborhood.

If you want to read more about the Local Bubble, there are papers and illustrations available with more details.