Experiments were conducted in reduced gravity aboard a parabolic aircraft. Credit: University of Straffordshire
While there’s still an incredible amount of science and work to do before living in space moves from fiction to reality, society is certainly gaining on that mission. NASA’s goals include developing technologies that can be used to live and work on not only Mars, but the moon as well.
And if there is ever going to be a permanent or even semi-permanent base in outer space, society needs to be prepared for the inevitable: humans committing crimes.
“As humanity’s footprint expands beyond the familiar terrains of Earth to the Moon and possibly beyond, an intriguing new field emerges from the final frontier: astroforensics. This discipline, still in its infancy, is propelled by the inevitability of human nature,” writes Zack Kowalske, bloodstain pattern analysis expert and current PhD researcher at Staffordshire University.
In a new study, Kowalske, Graham Williams, professor of forensic science at the University of Hull (UK), and colleagues explored how forensic science can be adapted to unforgiving extraterrestrial environments. Specifically, the team examined the behavior of blood in microgravity and the unique challenges of bloodstain pattern analysis aboard spacecraft.
“Unlike Earth, where gravity, a constant force, shapes many aspects of our reality, the significant reduction of gravity in space introduces novel challenges in understanding how evidence behaves,” write Kowalske and Williams in an article published in The Conversation. “This shift is crucial for forensic sciences like bloodstain pattern analysis, which relies heavily on gravitational effects to determine the circumstances under which blood stains are formed.”
For the study, published in Forensic Science International: Reports, Kowalske and his team conducted experiments aboard a Zero Gravity Corporation modified Boeing 727 parabolic aircraft. Colloquially referred to as the “vomit comet,” the parabolic flight research plane induces short periods of microgravity due to its up-and-down flight path.
During this 20-second period of freefalling microgravity between 0.00 and 0.05 g., researchers used a syringe to propel “blood” across 20 cm onto a sheet of white paper. Due to biohazard concerns, the team used a synthetic analogue of blood—a mixture of 40% glycerin and 60% red food coloring that stimulates the relative density and viscosity of human blood. The blood-stained papers were then photographed and analyzed per normal, Earth-borne procedures.
Unsurprisingly, the researchers noted that microgravity does indeed change the behavior of the blood drops and the stains they create. On Earth, blood tends to fall in a parabolic manner, with gravity pulling down on it until it strikes a surface. But in this case, the blood continued to travel in a straight line until it hit the surface. This straight-line flight path is a fluid example of inertia in action.
Additionally, the team saw a difference in the spreading action of the blood upon striking the surface. In the typical gravity environment of Earth, liquid blood drops will undergo a series of stages in the stain creation process. This entails the droplet’s collapse, the formation of a small wave, and the spread into a final stain shape. However, when gravity is eliminated from this action, the spreading action is inhibited by the dominating force of surface tension and cohesion, resulting in a stain shape and size that is smaller than its terrestrial twin.
“With the lack of gravitational influence, surface tension and cohesion of blood droplets are amplified,” explained Williams. “What this means is that blood in space has a higher tendency to stick to surfaces until a greater force causes detachment. Within the application of bloodstain formation, it means that blood drops exhibit a slower spread rate and, therefore, have shapes and sizes that would not be reflective on Earth.”
This is the first study relating to the behavior of blood in free flight; but Kowalske does not think it will be the last.
“We find ourselves in a new era of forensic science” he said. “Just as mid-19th century research asked the question of what a bloodstain meant in relation to cause, we are once again at the beginning of new questions that tie in how new environments influence forensic science. Astroforensics is a novel subdiscipline that is in its infancy. Broadening the understanding of all forensic sciences in non-terrestrial environments is critical as we expand into a space-faring species.”