A confined space, limited suspects, and no contact with the outside world: the perfect recipe for a classic murder mystery. Strangely enough, these are also the conditions aboard the International Space Station (ISS), where astronauts – carefully selected for their resourcefulness, stamina and near-impossible composure – spend months locked together.
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Of course, we like to imagine Earth’s finest scientists as above reproach, but who hasn’t, in moments of frustration, wondered about silencing a colleague? Extended stints in high-pressure settings can test anyone’s patience. Cosmonaut Valery Ryumin admitted as much in his 1980 diary, reflecting on his mission in orbit: “All the necessary conditions to perpetrate a murder are met by locking two men in a cabin of 5 x 6m [18 x 20ft] for two months.”
Should the unthinkable ever occur, investigators will need answers. Yet Earth-bound forensic techniques may not prove reliable in low-gravity environments. With private space travel edging closer, researchers are beginning to explore an emerging field: astroforensics. One major complication facing space detectives is gravity – or rather, the lack of it.
“Gravity is all pervasive around us – it’s the number-one environmental variable that we’re always dealing with,” explains Zack Kowalske, a forensic detective from Roswell Police Department in Georgia, USA.
His doctoral research into environmental effects on bloodstain analysis prompted an unusual question: what happens to blood spatter in microgravity?
Bloodstain pattern analysis combines physics, fluid dynamics and mathematics to calculate the angle of impact. On Earth, gravity ensures that blood droplets collapse and spread when they strike a surface, creating a pattern that reveals their trajectory. In orbit, things are far less straightforward.
To test his theory, Kowalske teamed up with Dr George Pantalos, a space medicine specialist at the University of Louisville. Together, they carried out experiments aboard a parabolic flight aircraft – better known as the ‘vomit comet’. During brief spells of weightlessness, Pantalos squirted synthetic blood onto paper. Instead of spreading into elongated stains, the droplets retained their shape, clinging tightly due to surface tension.
“When you remove gravity as a variable, the next predominant physical force that takes over is surface tension,” says Kowalske.
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The result? Smaller, uniform stains that reveal little about their origin. Investigators would struggle to determine whether a wound occurred in the ISS’s Cupola or in its central module. The experiments themselves weren’t without difficulty. Each microgravity period lasted only seconds before the aircraft surged into double gravity, distorting the stains immediately. The set-up also restricted the team to stains produced from a mere 20cm (7.8in) above the surface.
Another complication lies in trajectory. On Earth, droplets arc as gravity pulls them down. In space, they travel in a straight line until colliding with a surface. In the long corridors of the ISS, this makes tracing their origin even more challenging.
The research highlights just how complex a murder investigation in orbit would be. How do blood droplets interact with the constant airflow systems inside the ISS? How quickly would blood dry in microgravity? And would hydrophobic spacecraft materials alter how stains form? Equally, investigators could not rely on familiar clues such as pooling blood or trails of drips. A victim’s blood would remain suspended or cling to surfaces unpredictably, erasing many of the tell-tale signs used in traditional crime scenes.
For now, astroforensics remains a field in its infancy. Yet with human space travel expanding, the day may come when detectives must solve the ultimate locked-room mystery – not on Earth, but among the stars.
