Zapping a rodent's brain can put it into suspended animation. Scientists want to one day use the same technique for humans traveling to Mars.

• Scientists have zapped mice and rats into a suspended-animation-like state called torpor. 
• The state was induced by beaming ultrasound waves into a precise spot in the rodent's brains. 
• This technique could one day be used on humans for space travel and medical purposes.

Scientists have been able to induce a torpor state in mice and rats using ultrasound, bringing them a step closer to finding a way to induce suspended animation in humans. 

Space agencies like NASA and the European Space Agency (ESA) are eagerly awaiting science that artificially induces torpor or hibernation-like states in animals. 

They hope this could one day save on energy and costs of long-haul space travel to planets like Mars.

The latest study, published in the peer-reviewed journal Nature Metabolism, found researchers were able to induce torpor in mice and in rats using ultrasonic waves targeting a precise part of the animals' brains. 

"If successfully demonstrated in humans, this technology holds significant potential for medical applications, particularly in life-threatening conditions such as stroke and heart attacks," lead study author Hong Chen, a professor of biomedical engineering at Washington University, told Live Science.

"We could envision astronauts wearing a helmet-like device designed to target the hypothalamus region to induce a torpor-like state," she said.

Tiny helmets zap the rodents' brains

Torpor is a state of suspended animation whereby animals may look like they are going to sleep, but they are actually drastically reducing their metabolic activity, usually in response to extremely adverse conditions. 

Scientists had previously found that torpor can be triggered by injecting a chemical into a precise part of the brain that controls the central nervous system. But Chen and colleagues were interested to see if there was a non-invasive way to induce that state, without physically breaching the skull. 

Mice and rats were fitted with tiny helmets to send ultrasonic waves to the brain. The scientists observed that these waves were effectively able to push the rodents into a state of torpor.  

For about an hour after the ultrasound pulse, the mice's body temperatures and metabolism dropped, a state similar to torpor seen in nature. The mice's average body temperatures dropped by up to 6.25 degrees Fahrenheit (3.5 degrees Celsius) and their heart rate and oxygen usage dropped as well. 

The rats' body temperatures also dropped, though to a lesser level, up to 3.57 F (2 C). 

The fact that this state was triggered in rats is encouraging, as these rodents "do not naturally enter torpor, suggesting the possibility that similar effects could be induced in humans," the scientists said in the study.  

This technology could one day be used to make space travel more economical

Space agencies are keeping a close eye on this type of research. If they were able to crack the science of suspended animation, it could make space travel safer and cheaper, especially for long-haul flights like the 16-month-long round trip to Mars.

A single astronaut eats about 30 kilograms (66 pounds) of food and water a week, but their consumption could drop by 75% in suspended animation, per the BBC. Astronauts would also need much less space to roam around, so the rocket wouldn't need crew quarters.

Taken together, these cuts could save several tons of mass, a crucial saving when each pound adds weight to an already hefty rocket, ESA found in a 2019 study.

Inducing a hibernation-like state also has health benefits. Studies suggest astronauts would be at lesser risk of substantial muscle and bone density loss and protected from the worst effects of exposure to cosmic radiation. It could also protect the astronauts' mental health, as nobody knows what happens to human minds after being away from Earth for that long.

Hibernation in space would be "nowhere near as extreme as what we see in the movies," John Bradford, president and CTO of SpaceWorks Enterprises, previously told CNET. Spaceworks received several funding rounds from NASA in 2016 to develop a space hibernation concept. 

For Spaceworks, astronauts would be induced into torpor for 14 days at a time and woken for three or four days. That way, there would always be an active astronaut on shift to monitor proceedings. 

Scientists are getting closer, but aren't quite there

The rapid progress in the basic science to support this innovation is encouraging. 

One avenue to induce suspended animation is to cool the body down dramatically. In fact, surgeons are already using deep hypothermia — cooling the body temperature to under 95 degrees Fahrenheit (35 celsius) — to stop the blood during particularly tricky cardiac surgeries, though this should be done for more than 20 to 30 minutes. 

Other studies, like this recent one, suggest hacking the brain's dormant torpor mechanism to induce this state. Previous studies had suggested torpor could be induced with drugs, but the advantage of the approach in this recent study, is that it is noninvasive, precise, and safe, scientists said in the study. 

"As far as we know, there is nothing unique about homo sapiens that would prevent our species from hibernating, and I believe the capacity is there but it needs to be unlocked," Vladyslav Vyazovskiy, professor of sleep physiology at the University of Oxford, told the BBC.

"To me, the real question is not whether we can hibernate, but how… How do neurons in the hypothalamus 'know' that it is time to hibernate? Who tells them? This is the real question," he said.

Nevertheless, most of the research into long-ranging suspended animation is still only being done on animals, and we're likely still a long way away from testing it on humans.

"Further research is still required to determine the safety and feasibility of this approach in humans," Chen told Live Science.