Gravity Team studies how astronauts determine 'up' in space

International Space Station. Credits: ESA

Keeping upright in a low-gravity environment is not easy, and NASA documents abound with examples of astronauts falling on the lunar surface.

Now, a new study by an international team of researchers led by York University professors Laurence Harris and Michael Jenkin, published today in PLOS ONE, suggests that the reason for all these moon mishaps might be because its gravity isn't sufficient to provide astronauts with unambiguous information on which way is "up".

"The perception of the relative orientation of oneself and the world is important not only to balance, but also for many other aspects of perception including recognizing faces and objects and predicting how objects are going to behave when dropped or thrown," says Harris.

"Misinterpreting which way is up can lead to perceptual errors and threaten balance if a person uses an incorrect reference point to stabilize themselves."

Using a short-arm centrifuge provided by the European Space Agency, the international team simulated gravitational fields of different strengths, and used a York-invented perceptual test to measure the effectiveness of gravity in determining the perception of up.

The team found that the threshold level of gravity needed to just influence a person's orientation judgment was about 15 per cent of the level found on Earth, very close to that on the moon.

The team also found that Martian gravity, at 38 per cent of that on Earth, should be sufficient for astronauts to orient themselves and maintain balance on any future manned missions to Mars.

"If the brain does not sense enough gravity to determine which way is up, astronauts may get disoriented, which can lead to errors like flipping switches the wrong way or moving the wrong way in an emergency," says Jenkin.

"Therefore, it's crucial to understand how the direction of up is established and to establish the relative contribution of gravity to this direction before journeying to environments with gravity levels different to that of Earth."

This work builds upon results obtained in long-duration microgravity by Harris and Jenkin and other members of York's Centre for Vision Research on board the International Space Station during the Bodies in the Space Environment project, funded by the Canadian Space Agency.

More information: PLOS ONE, www.plosone.org/article/info%3… journal.pone.0106207

NASA Studies of the ultraviolet sun

Four of the telescopes on the Solar Dynamics Observatory observe extreme ultraviolet light activity on the sun that is invisible to the naked eye. 

Credit: NASA/SDO

You cannot look at the sun without special filters, and the naked eye cannot perceive certain wavelengths of sunlight.

Solar physicists must consequently rely on spacecraft that can observe this invisible light before the atmosphere absorbs it.

"Certain wavelengths either do not make it through Earth's atmosphere or cannot be seen by our eyes, so we cannot use normal optical telescopes to look at the spectrum," said Dean Pesnell, the project scientist for the Solar Dynamics Observatory (SDO), at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

Several spacecraft can observe these invisible light wavelengths. SDO for example has four telescopes that image the sun in the ultraviolet spectrum.

As beams of ultraviolet light pass into the telescope, a mirror with special coatings filters and amplifies the ultraviolet light's otherwise poor reflection.

The incoming photons are then recorded as pixels and converted into electrical signals, similar to how your cell phone camera sees visible light.

"It's exactly the same process, whether it's ultraviolet light, infrared light, visible light, or radio," said Joseph Gurman, project scientist for both the Solar and Heliospheric Observatory (SOHO) and the Solar Terrestrial Relations Observatory (STEREO) at Goddard.

"In this case we're trying to understand how the sun changes and how those changes affect life here on Earth."

Ultraviolet light causes molecular radiation damage to our skin, seen as sunburns that can lead to cancer.

Its cousin, extreme ultraviolet radiation, and the associated solar storms have the potential to disrupt communications and spacecraft navigation.

"These are very damaging, energetic photons, and we want to understand what chain of events produces these photons," Pesnell said.

The Solar Dynamics Observatory (SDO) observed a solar flare (upper left) and a coronal mass ejection (right) erupting from the sun’s limb in extreme ultraviolet light on August 6, 2010. 

Credit: NASA/SDO

Thankfully our planet's atmosphere absorbs much of this solar radiation, making life on Earth possible.

However, this means that to study extreme ultraviolet light, instruments must do it from the vacuum of space.

"Ultraviolet light from the sun can show us the origins of solar storms that can lead to power outages, cell phone disruptions, and delays in shipping packages due to the rerouting of planes from over the pole," Gurman said.

By understanding what occurs in the sun's atmosphere, scientists hope to predict when powerful solar events such as coronal mass ejections and solar flares may occur.

Spacecraft record solar activity as a binary code, 1s and 0s, which computer programs can translate into black and white. 

Scientists coloroured the images for realism, and then zoom in on areas of interest. 

Credit: NASA/Karen Fox

"You really want to know what's happening on the sun as soon as you can," said Jack Ireland, a solar visualization specialist at Goddard.

"We can then use computer models to estimate how solar events will affect Earth's space environment."

The information can then be used by NOAA's Space Weather Prediction Center, in Boulder, Co. to alert power companies and airlines to take the necessary precautions, thus avoiding power outages and keeping airplane passengers safe.