Astronauts to the moon

Humans sometimes have difficulty orienting themselves in a low-gravity environment. In this image from Dec. 12, 1972, NASA astronaut Jack Schmitt topples over after losing his balance during an Apollo 17 moonwalk.

Credit: NASA

Humans need at least 15 percent of the level of gravity found on Earth to orient themselves, according to findings published yesterday (Sept. 3) in the journal PLOS ONE. That means the level of gravity on the moon — about 17 percent of Earth's gravity — is just barely strong enough to provide adequate cues for astronauts to know which way is up.

No one has been back to the moon since Cernan and Schmitt blasted off the lunar surface in December 1972. But scientists have ways to simulate the low-gravity environment of the moon without leaving Earth.

Five men and five women participated in the experiment at the European Space Agency's Short Arm Centrifuge Facility (SAHC) in Cologne, Germany. The participants lied down on a platform in the human centrifuge with their feet facing away from the center. Depending on how fast the machine spun, the recruits experienced different levels of gravity, from 0g, close to the weightless environment in orbit, to 1g, the force humans feel while standing on Earth, explained study leader Laurence Harris of York University in Canada.

While whirling around in the centrifuge, the participants took a perceptual test, in which they had to choose whether the tilted letter they were looking at on a circular computer screen was a "p" or "d." In a near-zero-gravity environment, such as the International Space Station, astronauts need to rely on visual cues alone to orient themselves, Harris said. The results of the experiment found that gravity only starts influencing a person's sense of up and down once it hits about 0.15g.

"In a low gravitational field, such as on the moon, you'll have an unreliable estimate for what gravity's telling you is up, " Harris told Space.com. In retrospect, he said, it's not surprising that a YouTube search for "astronauts falling over" yields so many results.

It has been more than four decades since the first men landed on the moon on July 20, 1969. Test your memory of the moon landing with this quiz.

0 of 10 questions complete

Apollo Quiz: Test Your Moon Landing Memory

It has been more than four decades since the first men landed on the moon on July 20, 1969. Test your memory of the moon landing with this quiz.

0 of questions complete

Disoriented astronauts don't just risk tipping over. They might flip a switch the wrong way in an emergency, or misjudge how an object is going to behave when it's dropped or thrown. Apollo astronauts at the wheel of NASA's moon rovers reported that they had a hard time estimating the incline of the lunar terrain while driving. The findings suggest engineers building extraterrestrial cars probably will need to make sure they include an instrument in the dashboard that tells the pitch of the vehicle for astronaut drivers who are unable to rely on their own senses, Harris said.

"It's just really important that we understand our sensory systems before we go into extreme environments, " Harris said.

There is good news for space program managers with their sights set on Mars: With 38 percent of Earth's gravity, the Red Planet's gravity should be sufficient for astronauts to easily orient themselves and maintain balance, the researchers said.

Follow Megan Gannon on Twitter and Google+. Follow us @Spacedotcom, Facebook or Google+. Originally published on Space.com.

how many solutions does this have which manager won the most trophies what workers are exempt from overtime why project based learning how science works flowchart where apple products are made which device is i'm a window an example of where's device manager how far will technology advance what equipment does medicare pay for how much system data is normal on iphone how many solutions exist for the given equation how often should disinfectant solutions be changed how to explain a teacher where to design business cards who to hire first startup whose immune system is stronger when management wants you out how much entrepreneur make how often is frequent what start up means who solution recipe how workers comp works which london airport is closest to southampton how many business days in a year when system testing is performed how workers comp settlement is calculated who roadmap access to medicines what london station goes to cambridge how much startup money to open a restaurant how many products are made from corn which solutions would you use when design thinking started how much design cost how technology has changed education who solution focused brief therapy who roadmap snakebite where to donate technology near me how much equipment was left in syria how many workers in the us what workers are exempt from overtime where to solve math word problems where technology is headed where to find engineering research kenshi how engineering works manager who lead who developed the triarchic theory of intelligence what solutions are isotonic who design nazi uniforms why solution is considered as mixture who owns defi solutions how entrepreneur start a business who devised the trojan horse where to find engineering jobs how start up funding works where to build science nexus why tech stocks are falling today why device unreachable iphone where to get technology news which manager has the most ucl where tech companies are moving which startup is best in india how long system restore windows 10 what manufacturer does lululemon use how much project engineer make what startup companies to invest in why system design is important where teachers get paid the most how technology affects our lives where system of a down from whose autonomous system number how many technology companies in the world where to find roadmap in jira the de whose solution is y c 2 c x how often change solution contact what device did you plug in how many system in human body how much managers check bdo how many workers in the us startup who ends up with dalmi how much project manager salary when should you stop teaching where to buy tech deck how development affects environment how london became the center of the world which design is seen in the gummersmark brooch how far machine learning who management of pain whose product is mysql where is product key for microsoft office why engineering is important how much project managers make when boot up whose methodology of teaching experimentation is the key note of where is the source located where business meets fashion what entrepreneur mean whose project is the metro manila subway how many device disney plus what products are made from oil how much solution in vax platinum which solution is basic what design style am i what teaching means to me how much london visa cost what technology is most popular today how many manager in hotel when entrepreneurship is successful where is solutions store where to buy products in bulk how often do you use acapella device when solution of ni2 and nh3 when workers are asked to participate when product of inertia is zero where to find system ip address why product photography is important which technology is not a form of broadband why design thinking