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There are a couple potential explanations for distinctive markings found on a Martian rock, but new evidence suggests they are most likely to be related to microbial activity

The Starlab commercial space station project is moving toward the production phase, having passed a key development milestone with NASA.

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Preparations for Next Moonwalk Simulations Underway (and Underwater)

Skylab 3 astronauts witnessed many spectacular sights during their 858 orbital trips around the Earth in the summer of 1973. One involved watching powerful Hurricane Ellen take shape off the West African coast. “There’s a nice storm down there. She looks pretty big. She’s got a lot of clouds,” said astronaut Alan L. Bean upon viewing the storm from Skylab’s low-Earth orbit.

Knowing they were witnessing something of interest to meteorologists on Earth, Bean and his fellow Skylab crew members captured stereo photographs of the storm using cameras aboard the space station. Meteorologists later used these images, which provided three-dimensional data, to help them understand how the clouds in tropical systems formed and functioned.

This image of Hurricane Ellen was taken by Skylab astronauts in September 1973. Unscheduled weather observations that relied on the judgement and actions of Skylab astronauts captured valuable research data for scientists.NASA

Like the Skylab 3 crew’s photographs of Hurricane Ellen, the lightning observations of Skylab 4 astronaut Edward G. Gibson were also used by meteorologists to understand regional weather phenomena. While gazing down at a storm over South America’s Andes Mountains, Gibson noted that the thunderstorm he observed generated recognizable lightning patterns over a 500-square-mile region.

“A few things impressed me here: one is the fact that they could go off simultaneously or near simultaneously over a large distance—sympathetic lightning bolts, if you will, analogous to sympathetic flares on the sun. And that we do get periods of calm between periods of very high activity. Some sort of collective phenomenon appears to be at work,” Gibson recalled.

This photograph of Edward G. Gibson, Skylab 4 science pilot, was taken at Kennedy Space Center, Florida on November 8, 1973, before his November 16 launch to Skylab. Meteorologists were very interested in the regional lightning patterns he witnessed while aboard the space station.NASA

The photographs of Hurricane Ellen and Gibson’s notes about lightning patterns are just two of many valuable meteorological observations and recordings astronauts made during Skylab’s three crewed missions. All told, astronaut-conducted Earth studies provided important regional, also known as mesoscale, weather data that improved storm forecasting.

Along with providing valuable data to meteorologists, the notable findings of the Skylab astronauts supported the argument of the era’s scientists and mission planners who insisted that there was no adequate replacement for intelligent human observers in space.

Perhaps the authors of Living and Working in Space: A History of Skylab  put it best when they wrote: “Man’s ability to discriminate, to select the important features of a wide vista, and to respond effectively to unexpected events constituted his greatest contribution to orbital investigations.”

Read more about how Ed Gibson's lightning observations impacted weather forecasting Read the NASA publication Skylab Explores the Earth Share

Details Last Updated Mar 17, 2025 Related Terms

• NASA History
• Skylab
• Weather and Atmospheric Dynamics

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Atomic Layer Processing Coating Techniques Enable Missions to See Further into the Ultraviolet

Astrophysics observations at ultraviolet (UV) wavelengths often probe the most dynamic aspects of the universe. However, the high energy of ultraviolet photons means that their interaction with the materials that make up an observing instrument are less efficient, resulting in low overall throughput. New approaches in the development of thin film coatings are addressing this shortcoming by engineering the coatings of instrument structures at the atomic scale.

Researchers at the NASA Jet Propulsion Laboratory (JPL) are employing atomic layer deposition (ALD) and atomic layer etching (ALE) to enable new coating technologies for instruments measuring ultraviolet light. Conventional optical coatings largely rely on physical vapor deposition (PVD) methods like evaporation, where the coating layer is formed by vaporizing the source material and then condensing it onto the intended substrate. In contrast, ALD and ALE rely on a cyclic series of self-limiting chemical reactions that result in the deposition (or removal) of material one atomic layer at a time. This self-limiting characteristic results in a coating or etchings that are conformal over arbitrary shapes with precisely controlled layer thickness determined by the number of ALD or ALE cycles performed.

The ALD and ALE techniques are common in the semiconductor industry where they are used to fabricate high-performance transistors. Their use as an optical coating method is less common, particularly at ultraviolet wavelengths where the choice of optical coating material is largely restricted to metal fluorides instead of more common metal oxides, due to the larger optical band energy of fluoride materials, which minimizes absorption losses in the coatings. Using an approach based on co-reaction with hydrogen fluoride, the team at JPL has developed a variety of fluoride-based ALD and ALE processes.

(left) The Supernova remnants and Proxies for ReIonization Testbed Experiment (SPRITE) CubeSat primary mirror inside the ALD coating facility at JPL, the mirror is 18 cm on the long and is the largest optic coated in this chamber to-date. (right) Flight optic coating inside JPL ALD chamber for Pioneers Aspera Mission. Like SPRITE, the Aspera coating combines a lithium fluoride process developed at NASA GSFC with thin ALD encapsulation of magnesium fluoride at JPL. Image Credit: NASA-JPL

In addition to these metal-fluoride materials, layers of aluminum are often used to construct structures like reflective mirrors and bandpass filters for instruments operating in the UV.  Although aluminum has high intrinsic UV reflectance, it also readily forms a surface oxide that strongly absorbs UV light. The role of the metal fluoride coating is then to protect the aluminum surface from oxidation while maintaining enough transparency to create a mirror with high reflectance.

The use of ALD in this context has initially been pursued in the development of telescope optics for two SmallSat astrophysics missions that will operate in the UV: the Supernova remnants and Proxies for ReIonization Testbed Experiment (SPRITE) CubeSat mission led by Brian Fleming at the University of Colorado Boulder, and the Aspera mission led by Carlos Vargas at the University of Arizona. The mirrors for SPRITE and Aspera have reflective coatings that utilize aluminum protected by lithium fluoride using a novel PVD processes developed at NASA Goddard Space Flight Center, and an additional very thin top coating of magnesium fluoride deposited via ALD.

Team member John Hennessy prepares to load a sample wafer in the ALD coating chamber at JPL. Image Credit: NASA JPL

The use of lithium fluoride enables SPRITE and Aspera to “see” further into the UV than other missions like NASA’s Hubble Space Telescope, which uses only magnesium fluoride to protect its aluminum mirror surfaces. However, a drawback of lithium fluoride is its sensitivity to moisture, which in some cases can cause the performance of these mirror coatings to degrade on the ground prior to launch. To circumvent this issue, very thin layers (~1.5 nanometers) of magnesium fluoride were deposited by ALD on top of the lithium fluoride on the SPRITE and Aspera mirrors. The magnesium fluoride layers are thin enough to not strongly impact the performance of the mirror at the shortest wavelengths, but thick enough to enhance the stability against humidity during ground phases of the missions. Similar approaches are being considered for the mirror coatings of the future NASA flagship Habitable Worlds Observatory (HWO).

Multilayer structures of aluminum and metal fluorides can also function as bandpass filters (filters that allow only signals within a selected range of wavelengths to pass through to be recorded) in the UV. Here, ALD is an attractive option due to the inherent repeatability and precise thickness control of the process. There is currently no suitable ALD process to deposit aluminum, and so additional work by the JPL team has explored the development of a custom vacuum coating chamber that combines the PVD aluminum and ALD fluoride processes described above. This system has been used to develop UV bandpass filters that can be deposited directly onto imaging sensors like silicon (Si) CCDs. These coatings can enable such sensors to operate with high UV efficiency, but low sensitivity to longer wavelength visible photons that would otherwise add background noise to the UV observations.

Structures composed of multilayer aluminum and metal fluoride coatings have recently been delivered as part of a UV camera to the Star-Planet Activity Research CubeSat (SPARCS) mission led by Evgenya Shkolnik at Arizona State University. The JPL-developed camera incorporates a delta-doped Si CCD with the ALD/PVD filter coating on the far ultraviolet channel, yielding a sensor with high efficiency in a band centered near 160 nm with low response to out-of-band light.

A prototype of a back-illuminated CCD incorporating a multi-layer metal-dielectric bandpass filter coating deposited by a combination of thermal evaporation and ALD. This coating combined with JPL back surface passivation approaches enable the Si CCD to operate with high UV efficiency while rejecting longer wavelength light. Image credit: NASA JPL

Next, the JPL team that developed these coating processes plans to focus on implementing a similar bandpass filter on an array of larger-format Si Complementary Metal-Oxide-Semiconductor (CMOS) sensors for the recently selected NASA Medium-Class Explorer (MIDEX) UltraViolet EXplorer (UVEX) mission led by Fiona Harrison at the California Institute of Technology, which is targeted to launch in the early 2030s. 

For additional details, see the entry for this project on NASA TechPort

Project Lead: Dr. John Hennessy, Jet Propulsion Laboratory (JPL)

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Mar 18, 2025

Related Terms

• Technology Highlights
• Astrophysics
• Astrophysics Division
• Jet Propulsion Laboratory
• Science-enabling Technology

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