A confined space, a limited number of suspects, a lack of contact with the outside world. These are the makings of a juicy murder mystery.
They’re also eerily similar to conditions aboard the International Space Station (ISS), where astronauts – highly trained personnel selected for their resourcefulness, endurance and almost impossibly cool composure – spend months on end trapped together.
Though we like to think of Earth’s best and brightest scientists as incorruptible, who hasn’t considered murdering a co-worker from time to time? And extended stays in high-stress environments are enough to make anyone snap.
As cosmonaut Valery Ryumin chillingly wrote in his personal diary during a stint in space in 1980: “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.”
In the worst-case scenario where something gruesome does happen in space, we’ll want to know who did it. But we’re starting off with a disadvantage: the forensic methods we’ve developed on Earth won’t necessarily cut it in the face of low-gravity, off-planet environments.
With civilian space travel on the horizon, some experts are calling for investment in the emerging field of astroforensics – and the first research in this area has already landed.
So, awkwardly pull on a trench coat over your spacesuit and perch a fedora on your helmet, because it’s time to go crime-solving… in space.
Houston, we have a homicide
One thing investigators are sure to notice missing in their first extraterrestrial case? Gravity.
“Gravity is all pervasive around us – it’s the number-one environmental variable that we’re always dealing with,” says Zack Kowalske, a forensic detective in the Crime Scene Investigations (CSI) Unit at Roswell Police Department in Georgia, in the US.
His PhD research, on how environmental factors influence forensic bloodstain analysis, led him to a rather unusual question: how would blood spatter patterns change in low or zero gravity?
Bloodstain pattern analysis is a crucial forensic tool that uses fluid dynamics, physics and mathematics to calculate the trajectory of blood droplets to understand how they hit a surface. On Earth, gravity influences that pattern. In space, however…
We generally think of space as having no gravity. But astronauts on the ISS experience microgravity, which causes weightlessness even though at the station’s altitude, gravity is still about 90 per cent of the strength as here on Earth. That’s because the station’s orbit keeps it in a state of constant falling.
To conduct the first-ever investigation of blood stains in microgravity, Kowalske collaborated with Dr George Pantalos, a researcher specialising in space medicine at the University of Louisville.
They performed the experiment on a parabolic flight research plane (colloquially known as a ‘vomit comet’), which alternates between soaring up and diving down to generate short periods of microgravity. During the freefall period of the flight, Pantalos used a syringe to squirt synthetic blood onto a piece of paper.
Bloodstain analysts try to calculate the angle at which blood droplets struck a surface – known as the angle of impact – so that they can reconstruct where the blood came from.
Unfortunately for future space detectives, it turns out that gravity is a key component in deciphering these gruesome stains.
On Earth, when a droplet of blood strikes a flat surface, the droplet collapses and spreads out in such a way that it can be used to determine the angle of impact. The experiment performed aboard the vomit comet revealed that, without gravity, the surface tension of the droplets stops the blood from spreading across the surface.
“When you remove gravity as a variable, the next predominant physical force that takes over is surface tension,” says Kowalske.
Without the spread, you’re essentially left with a smaller bloodstain of questionable origins. Did the astronaut get stabbed in the ISS’s core module or while coming out of the Cupola? The tiny blood puddles on the walls will leave space detectives scratching their heads.
Conducting this pioneering research wasn’t without its challenges, Kowalske says – especially when the parabolic flight returns to Earth. “As soon as that microgravity arc is over, you then go into double gravity, so your stains immediately get ruined,” he explains.
And, because of the confined space in the research aircraft, they could only investigate blood stains created just 20cm (7.8in) from the paper.
It’s also worth noting that blood droplets have a curved trajectory on Earth, where gravity is pulling them down. In zero-g, though, blood will travel in a straight line, indefinitely, until it hits a surface.
“Inertia is going to keep these liquid drops on a straight flight path,” Kowalske says.
Given the long, straight modules of the ISS, this could make tracking down their point of origin even trickier. The study is an important first step towards developing accurate forensic methods for microgravity environments, but many unanswered questions remain.
Would the trajectory of blood droplets be influenced by the air currents that circulate oxygen around the closed environment of the ISS? How does blood dry in microgravity? And would the high-tech materials used inside the spacecraft have an impact on crime scene investigations?
Many of these surfaces are water-repelling, or ‘hydrophobic’, which would further alter how blood droplets land on a surface in space.
Dealing with blood in other areas of evidence will be different as well. For example, a victim’s blood wouldn’t pool on the ground and, if the murderer moved around, it wouldn’t leave a trail of telling drips behind them. No need for that magnifying glass, then.
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Ballistics report
So, suppose there’s a large amount of untraceable blood splattered over the walls of the ISS – now what? Space detectives will be on the hunt for a murder weapon.
Thankfully, a gunshot on the ISS would create similar evidence as it does here on Earth. When a gun is fired, the explosive reaction inside the chamber creates a “plume of gases and residues”.
These then condense into liquid droplets and solid particles that gradually settle and cover the crime scene, says Dr Chris Shepherd, a forensic ballistics expert at the University of Kent, in the UK.
These gunshot residues would cover the gun, the person who fired it, the victim and the crime scene. And it would be much harder for the shooter to clean away that type of evidence on the ISS, where astronauts wash with a sponge and soap, rather than showering.
Airborne residues “would persist in the atmosphere of the space station for a significant time,” Shepherd explains. They would eventually be sucked up into the station’s ventilation system and would probably be caught in filters that keep the air safe and breathable for the ISS crew.
Space crime scene investigators could then analyse these residues to determine the type of ammunition used.
Even here on Earth, gunshot residue analysis is a tricky business.
“Understanding how gunshot residues transfer between items [and] how long they persist in different environments – that’s something that we still don’t properly understand down here and I think it would be an even bigger challenge up there,” says Shepherd.
Experts think it’s likely that firing a gun on the ISS would create the same ballistic fingerprint on the bullet and inside the barrel of the gun as it does on Earth, and these unique markings could be used to link a bullet to a weapon. But for obvious safety reasons, the ISS lacks a shooting range.
This complicates the job of ballistics experts, who wouldn’t be able to reconstruct the shooting under the same conditions they were fired under.
Microgravity would also interfere with bullets – once fired, they’d continue in infinite straight lines, instead of a trajectory curved by Earth’s gravity. In the relatively confined space of the ISS, however, a shooting is likely to be close-range, so the lack of gravity wouldn’t interfere too much.
The bullet would probably end up stuck in the ultra-thick walls of the space station, or bounce off them and then float around inside the cabin.
That said, a gun probably isn’t the best choice of weapon if you wanted to commit a murder in space. “I don’t think that would be the best way to go – there’d be a lot of very obvious evidence,” says Shepherd.
Dusting for prints
nap on your rubber gloves – it’s time to track down the murderers’ DNA. The closed environment of the ISS could work in favour of forensic investigators in this case. Trace evidence, such as hairs or fibres, would stay on board – either at the crime scene, or trapped inside air or water filters.
“Having a closed system could be advantageous because everything is filtered and collected, so the evidence would remain and be difficult to dispose of,” says Dr Valerie Ryder, Toxicology Lead at NASA’s Johnson Space Center.
Better rush it to the crime lab quickly, though. DNA evidence – the gold standard in forensic investigations – is likely to degrade faster in space due to the higher levels of solar radiation.
Though we don’t currently know how long such evidence lasts on the ISS, one study has found that DNA placed on the outside of a research rocket survived launch, spaceflight and re-entry into Earth’s atmosphere, despite being exposed to solar radiation and extremely high temperatures.
Assuming the ISS killer wasn’t wearing a spacesuit or gloves, they’d also deposit fingerprints on surfaces in the spacecraft, just like they would on Earth. But collecting that evidence would present novel challenges.
Traditional fingerprinting uses carbon or metal-based powders, which are dusted onto a surface and stick to the moisture left behind by a person’s fingers. Another method involves releasing fumes from a heated glue onto the surface, which bonds to the fingerprints.
Perform these investigations in microgravity, though, and the fine dust and gases would become suspended in the air, remaining on the ISS indefinitely. This could potentially become a hazard to the crew.
Space murderers beware though. Fingerprinting in space isn’t impossible. Astroforensics teams could potentially rely on laser scanners or ultraviolet light to collect your prints (although this hasn’t yet been tested on the ISS).
Everyone’s a suspect
With all these unknowns in the mix and astroforensics still developing as a field, what would investigators do if a murder on the ISS happened tomorrow?
For starters, microgravity and the recycling of air and water on the space station would make it very difficult to avoid contaminating a crime scene.
The onboard laboratory would come in handy, giving investigators access to plenty of equipment to process evidence from the crime. They’d be able to use the scanning electron microscopes to analyse gunshot residue, mass spectrometers to identify toxic substances and sequencing equipment to identify a suspect’s DNA.
But investigators would still be limited in their analysis and would have to send samples back to Earth for concrete conclusions.
It would also be extremely challenging to conduct an autopsy in microgravity because – you guessed it – bodily fluids would escape and float into the air.
Astronauts also suffer from reduced bone mineral density due to microgravity and this could alter impact patterns, making it more difficult to identify the murder weapon.
Another major unknown is how different types of evidence might change and degrade over time on a spacecraft.
“[On Earth] how we measure how much time has passed between an event and a consequence is determined by environmental factors. These either behave differently or don’t exist the same way in space,” says Dr Mehzeb Chowdhury, a criminologist and criminal law barrister at Northumbria University.
Time of death would also be particularly difficult to determine.
Forensic scientists use several lines of evidence to estimate when death occurred. On Earth, blood starts to pool in the body as soon as the heart stops beating and these pooling patterns are used to estimate the time of death.
But in low- or zero-gravity conditions, blood might distribute more evenly throughout the body.
On Earth, a dead body goes through a predictable sequence of decay because of active microbes and invertebrates. If the location of the body is known, the state of decay can be used to generate a remarkably accurate estimate of when death occurred.
But on the ISS, there are far fewer microbes and essentially no decomposing invertebrates around. This means a space murder victim’s body would decay much more slowly, making it harder to determine the time of death.
Considering all these factors, a conniving murderer could take advantage of the uncertainty around the timing of events to create an alibi or frame someone else.
Another major challenge for space detectives would be impartiality. Initially, everyone would be a suspect, but they’d also be the only people available to collect evidence and investigate the crime.
That’s why “we need to leverage things like robotics [and] artificial intelligence, and be able to record evidence in non-traditional ways,” says Chowdhury. “Otherwise, any kind of investigation or outcome that comes from it will be tainted.”
In 2016, as a PhD student at Durham University, Chowdhury developed a remote imaging robot called MABMAT, designed to collect 360° videos and photographs at difficult-to-access crime scenes.
This type of system could also be equipped with high-resolution 3D fingerprinting technology or hyperspectral imaging to detect evidence that’s not visible to the naked eye.
Chowdhury believes robots like MABMAT will become astroforensic investigators’ trusty sidekicks, allowing “Earth-based experts to study dynamic, four-dimensional crime scenes, taking into account space, motion and time, long after the physical environment had changed.”
Ultimately, research into the field of astroforensics has only just begun and many unanswered questions remain. That’s why experts are urging space agencies to start investing in the tools to solve extraterrestrial crimes now. “We really need to have dedicated research in this area,” says Chowdhury.
As more people spend extended periods of time in space, it’s a tragic reality that crimes will become unavoidable. “We are, by nature, a very violent species, so it’s not unreasonable to hypothesise that we’ll be a violent species out among the stars,” says Kowalske.
In other words, it’s essential that when the first off-planet crimes happen, space Starsky and Hutch have the tools they need to conduct a rigorous and impartial investigation, bringing justice to the Solar System and beyond…
About our experts
Zack Kowalske is a forensic detective in the Crime Scene Investigations (CSI) Unit at Roswell Police Department in Georgia, in the US. He also has PhD research in forensic bloodstain analysis. He has been published in the likes of Forensic Science International: Reports, Journal of Forensic Sciences and Journal of Forensic Identification.
Dr Chris Shepherd is a forensic ballistics expert at the University of Kent, in the UK. He has been published in various scientific journals including Science & Justice: Journal of the Forensic Science Society, International Journal of Legal Medicine and Journal of Forensic Sciences.
Dr Valerie Ryder is the Toxicology Lead at NASA’s Johnson Space Center, in the US. She’s been published in the likes of Scientific Reports, Inhalation Toxicology and Aerospace Medical Association.
Dr Mehzeb Chowdhury is a criminologist and criminal law barrister at Northumbria University, in the UK. He is published in International Journal of Police Science and Management, Salus and Science and Justice.
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