In the red-band trailer for the new Mortal Kombat movie, the cryomancer ninja Sub-Zero (Joe Taslim) pulls off a stupidly cool move in his fight against his mortal (get it) enemy, the undead ninja Scorpion (Hiroyuki Sanada). In one fluid motion, Sub-Zero dodges Scorpion’s attack, slices his chest open, and then uses his powers to flash-freeze the spray of blood into a blood-icicle. My guy stabs Scorpion with his own frozen blood! In a just world, this alone would be enough to merit a Best Picture win for Mortal Kombat (hey, they expanded that category for a reason).
It will not, however, be winning any awards for scientific accuracy, because it turns out frozen blood wouldn’t make for a very effective weapon, even assuming you had a means to instantly turn fresh blood into a frosty crimson dagger. “My answer is no, you could not kill someone with a blood icicle,” Kimberlee Sue Moran, an Associate Teaching Professor & Director of Forensics at Rutgers University, tells Vulture. Moran, who is no stranger to engaging with absurd pop-culture what-ifs, is happy to pull off a fatality on our dreams of doing blood-icicle combat for a number of reasons — but basically, it comes down to debunking the old story of “the perfect crime” of killing somebody with a normal, non-blood icicle.
“A blood icicle would be almost exactly the same as a normal icicle because the vast majority of your blood is made out of water,” Moran explains. “It would be like taking a gallon of water and throwing a container of glitter in it. That’s basically what your blood is. It’s water with all of these red blood cells and a few white blood cells swirling around.”
Blood behaves basically the same as water would, for our purposes; it freezes at almost the same temperature — three degrees Celsius colder, to be precise. If Sub-Zero has mystic freezing properties (something that’s not even worth trying to explain with science, for obvious reasons), creating the bloody icicle wouldn’t be too much trickier than creating a basic water one.
“He would cool blood from normal body temperature down to below zero” Moran notes. “I guess Sub-Zero is a very fitting name.”
Your standard icicle is also very smooth and slippery, which could present an additional problem for whoever was trying to grip it to deliver a killing blow. Sub-Zero freezes the spray in mid-air, however, so it’s rough and jagged, meaning he’d be able to get a better grip on it. This is about where the good news for Sub-Zero stops, however, because the biggest issue is simply that ice is just too brittle.
“You’re putting it under a lot of force in order to pierce the skin. It’s going to shatter,” Moran says. “It’s not a super-strong material in terms of piercing skin, which is going to be pretty robust. Our skin is meant to withstand quite a lot of pressure.”
(Without being prompted, Moran conceded that stabbing somebody in the eye would “probably be more effective” because “the eye is just a sack of fluid” … Vulture digresses.)
Sub-Zero’s mastery of all things cold wouldn’t improve the structural stability of his bloody ice blade, either. Moran cites a 2015 study on the mechanical properties of ice that came to the conclusion that ice is at its strongest at around -35 degrees Celcius, and even then it’s not all that tough. If Sub-Zero lowered the temperature even more, his ice-blade would be able to withstand even less pressure, so this isn’t a situation where colder is necessarily better.
Moran also cites another study that aimed to answer a somewhat niche theory in archeology — that prehistoric man, without access to any sort of stone, might have used cold ice-age temperatures to freeze their own poop into tools. The scientists attempted to re-create these fecal tools, but the resulting blades were too shitty (sorry, sorry, trying to delete it) to work. They just couldn’t get sharp enough. Moran says frozen blood would fail on a similar level.
“You’ve got a point, but it’s unlikely it’s actually going to be sharp enough to actually break the skin,” she says.
Bludgeoning somebody with a heavy-enough ice club could inflict some damage, Moran concedes, but, unprompted, she suggests yet another more effective method of killing via ice. “I would just drop a giant glacier on somebody instead rather than hit them over the head with an icicle.”
“What would be far more useful would be to freeze the blood while it’s in the body,” Moran continues, again without having been teed up. “I’m sure you’ve seen the experiments of where you drop a rubber ball into a vat of liquid nitrogen and take it out and it smashes into pieces. You could do that instead.”
If you’ve played any Mortal Kombat video games, you know that that’s exactly what Sub-Zero frequently does when he finishes off a defeated opponent. It’s a graphic, effective fatality, but according to science, he should just lead with that one. It’s a lot more effective than making a dagger with frozen blood.