Gecko grippers get a microgravity test flight

There are no garbage trucks equipped to leave the atmosphere and pick up debris floating around Earth. But what if we could send a robot to do the job?

Scientists at NASA's Jet Propulsion Laboratory in Pasadena, California, are working on adhesive gripping tools that could grapple objects such as orbital debris or defunct satellites that would otherwise be hard to handle.

The gecko gripper project was selected for a test flight through the Flight Opportunities Program of NASA's Space Technology Mission Directorate. As a test, researchers used the grippers in brief periods of weightlessness aboard NASA's C-9B parabolic flight aircraft in August.

"Orbital debris is a serious risk to spacecraft, including the International Space Station," said Aaron Parness, a JPL robotics researcher who is the principal investigator for the grippers. "This is definitely a problem we're going to have to deal with. Our system might one day contribute to a solution."

The gripping system developed by Parness and colleagues was inspired by geckos, lizards that cling to walls with ease. Geckos' feet have branching arrays of tiny hairs, the smallest of which are hundreds of times thinner than a human hair. This system of hairs can conform to a rough surface without a lot of force. Although researchers cannot make a perfect replica of the gecko foot, they have put "hair" structures on the adhesive pads of the grippers.

The synthetic hairs, also called stalks, are wedge-shaped and have a slanted, mushroom-shaped cap. When the gripping pad lightly touches part of an object, only the very tips of the hairs make contact with that surface.

"The stickiness of the grippers can be turned on and off, by changing the direction in which you pull the hairs," Parness said.

To get the gripper to stick to a surface, force is applied to the adhesive pad material in a manner that makes the hairs bend. This increases the real area of contact between the hairs and the surface, which corresponds to greater adhesion. When the force is relaxed and the hairs go back to being upright, this process turns off the stickiness.

A phenomenon called van der Waals forces, named for Nobel Prize-winning physicist Johannes Diderik van der Waals, explains the non-permanent stickiness of the grippers, as well as gecko feet. These temporary adhesive forces happen because electrons orbiting the nuclei of atoms are not evenly spaced, creating a slight electrical charge. Such forces persist even in extreme temperature, pressure and radiation conditions.

"The reliability of van der Waals forces, even in severe environments, makes them particularly useful for space applications," Parness said.

"The system could grapple objects in space that are spinning or tumbling, and would otherwise be hard to target," he said.

In the recent tests, the grippers were able to grapple a 20-pound cube as it floated. The grippers also were able to grapple a researcher wearing a vest made of spacecraft material panels, representing a 250-pound "object." Members of the research team held the device with adhesive pads during the test, but the eventual idea is to integrate the grippers into a robotic arm or leg.

In total, the grippers have been tested on more than 30 spacecraft surfaces at JPL. They also have been tested successfully in a JPL thermal vacuum chamber, with total vacuum conditions and temperatures of minus 76 degrees Fahrenheit (minus 60 degrees Celsius) to simulate the conditions of space. While Parness was in graduate school at Stanford University in Palo Alto, California, the grippers were tested separately in more than 30,000 cycles of "on" and "off," with the adhesive staying strong. Several prototypes have since been designed.

There are more than 21,000 pieces of orbital debris larger than 3.9 inches (10 centimeters) in Earth's orbit. The U.S. Space Surveillance Network routinely tracks these objects. In 2009, an accidental collision occurred between an operational communications satellite and a large piece of debris, destroying the satellite.

Besides grappling orbital debris, the grippers could help inspect spacecraft or assist small satellites in docking to the International Space Station. The grippers are another example of how technology drives exploration.

The California Institute of Technology manages JPL for NASA.

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Scientists 'map' water vapor in Martian atmosphere

This graphs shows the latitudinal distribution of humidity in Mars' atmosphere during the year according to data collected by the SPICAMInfrared instruments.

Russian scientists from the Space Research Institute of the Russian Academy of Sciences and the Moscow Institute of Physics and Technology (MIPT), together with their French and American colleagues, have created a 'map' of the distribution of water vapour in Mars' atmosphere. Their research includes observations of seasonal variations in atmospheric concentrations using data collected over ten years by the Russian-French SPICAM spectrometer aboard the Mars Express orbiter. This is the longest period of observation and provides the largest volume of data about water vapour on Mars.

The first SPICAM (Spectroscopy for Investigation of Characteristics of the Atmosphere of Mars) instrument was built for the Russian Martian orbiter Mars 96, which was lost due to an accident in the rocket launcher.

The new updated version of the instrument was built with the participation of the Space Research Institute as part of the agreement between RosCosmos and the French space agency CNES for the Mars Express orbiter. The apparatus was launched on June 2, 2003 from the Baikonur Cosmodrome using a Russian Soyuz rocket launcher with a Fregat propulsion stage. At the end of December 2003, Mars Express entered a near-Mars orbit and since then has been operating successfully, collecting data on the planet and its surroundings.

Staff of the Space Research Institute and MIPT, including Alexander Trokhimovsky, Anna Fyodorova, Oleg Korablyov and Alexander Rodin, together with their colleagues from the French laboratory LATMOS and NASA's Goddard Center, have analysed a mass of data obtained by observing water vapour in Mars' atmosphere using an infrared spectrometer that is part of the SPICAM instrument over a period of five Martian years (about 10 Earth years as a year on Mars is equal to 1.88 Earth years).

Conditions on Mars -- low temperatures and low atmospheric pressure -- do not allow water to exist in liquid form in open reservoirs as it would on Earth. However, on Mars, there is a powerful layer of permafrost, with large reserves of frozen water concentrated at the polar caps. There is water vapour in the atmosphere, although at very low levels compared to the quantities experienced hereon Earth. If the entire volume of water in the atmosphere was to be spread evenly over the surface of the planet, the thickness of the water layer would not exceed 10-20 microns, while on Earth such a layer would be thousands of times thicker.

Data from the SPICAM experiment has allowed scientists to create a picture of the annual cycle of water vapour concentration variation in the atmosphere. Scientists have been observing the atmosphere during missions to Mars since the end of the 1970s in order to make the picture more precise, as well as traceits variability.

The content of water vapour in the atmosphere reaches a maximum level of 60-70 microns of released water in the northern regions during the summer season. The summer maximum in the southern hemisphere is significantly lower -- about 20 microns. The scientists have also established a significant, by 5-10 microns, reduction in the concentration of water vapour during global sandstorms, which is probably connected to the removal of water vapour from the atmosphere due to adsorption processes and condensation on surfaces.

"This research, based on one of the longest periods of monitoring of the Martian climate, has made an important contribution to the understanding of the Martian hydrological cycle -- the most important of the climate mechanisms which could potentially support the existence of biological activity on the planet," said co-author of the research Alexander Rodin, deputy head of the Infrared Spectroscopy of Planetary Atmospheres Laboratory at MIPT and senior scientific researcher at the Space Research Institute.

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NASA's MAVEN mission identifies links in chain leading to atmospheric loss

NASA’s MAVEN mission is observing the upper atmosphere of Mars to help understand climate change on the planet. MAVEN entered its science phase on Nov. 16, 2014.

Early discoveries by NASA's newest Mars orbiter are starting to reveal key features about the loss of the planet's atmosphere to space over time.

The findings are among the first returns from NASA's Mars Atmosphere and Volatile Evolution (MAVEN) mission, which entered its science phase on Nov. 16. The observations reveal a new process by which the solar wind can penetrate deep into a planetary atmosphere. They include the first comprehensive measurements of the composition of Mars' upper atmosphere and electrically charged ionosphere. The results also offer an unprecedented view of ions as they gain the energy that will lead to their to escape from the atmosphere.

"We are beginning to see the links in a chain that begins with solar-driven processes acting on gas in the upper atmosphere and leads to atmospheric loss," said Bruce Jakosky, MAVEN principal investigator with the Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder. "Over the course of the full mission, we'll be able to fill in this picture and really understand the processes by which the atmosphere changed over time."

On each orbit around Mars, MAVEN dips into the ionosphere -- the layer of ions and electrons extending from about 75 to 300 miles above the surface. This layer serves as a kind of shield around the planet, deflecting the solar wind, an intense stream of hot, high-energy particles from the sun.

Scientists have long thought that measurements of the solar wind could be made only before these particles hit the invisible boundary of the ionosphere. MAVEN's Solar Wind Ion Analyzer, however, has discovered a stream of solar-wind particles that are not deflected but penetrate deep into Mars' upper atmosphere and ionosphere.

Interactions in the upper atmosphere appear to transform this stream of ions into a neutral form that can penetrate to surprisingly low altitudes. Deep in the ionosphere, the stream emerges, almost Houdini-like, in ion form again. The reappearance of these ions, which retain characteristics of the pristine solar wind, provides a new way to track the properties of the solar wind and may make it easier to link drivers of atmospheric loss directly to activity in the upper atmosphere and ionosphere.

MAVEN's Neutral Gas and Ion Mass Spectrometer is exploring the nature of the reservoir from which gases are escaping by conducting the first comprehensive analysis of the composition of the upper atmosphere and ionosphere. These studies will help researchers make connections between the lower atmosphere, which controls climate, and the upper atmosphere, where the loss is occurring.

The instrument has measured the abundances of many gases in ion and neutral forms, revealing well-defined structure in the upper atmosphere and ionosphere, in contrast to the lower atmosphere, where gases are well-mixed. The variations in these abundances over time will provide new insights into the physics and chemistry of this region and have already provided evidence of significant upper-atmospheric "weather" that has not been measured in detail before.

New insight into how gases leave the atmosphere is being provided by the spacecraft's Suprathermal and Thermal Ion Composition (STATIC) instrument. Within hours after being turned on at Mars, STATIC detected the "polar plume" of ions escaping from Mars. This measurement is important in determining the rate of atmospheric loss.

As the satellite dips down into the atmosphere, STATIC identifies the cold ionosphere at closest approach and subsequently measures the heating of this charged gas to escape velocities as MAVEN rises in altitude. The energized ions ultimately break free of the planet's gravity as they move along a plume that extends behind Mars.

The MAVEN spacecraft and its instruments have the full technical capability proposed in 2007 and are on track to carry out the primary science mission. The MAVEN team delivered the spacecraft to Mars on schedule, launching on the very day in 2013 projected by the team 5 years earlier. MAVEN was also delivered well under the confirmed budget established by NASA in 2010.

The team's success can be attributed to a focused science mission that matched the available funding and diligent management of resources. There were also minimal changes in requirements on the hardware or science capabilities that could have driven costs. It also reflects good coordination between the principal investigator; the project management at NASA's Goddard Space Flight Center; the Mars Program Office at NASA's Jet Propulsion Laboratory in Pasadena, California; and the Mars Exploration Program at NASA Headquarters.

The entire project team contributed to MAVEN's success to date, including the management team, the spacecraft and science-instrument institutions, and the launch-services provider.

"The MAVEN spacecraft and its instruments are fully operational and well on their way to carrying out the primary science mission," said Jim Green, director of NASA's Planetary Science Division at NASA Headquarters in Washington. "The management team's outstanding work enabled the project to be delivered on schedule and under budget."

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