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By NASA
2 min read
NASA-Funded Study Examines Tidal Effects on Planet and Moon Interiors
NASA-supported scientists have developed a new method to compute how tides affect the interiors of planets and moons. Importantly, the new study looks at the effects of body tides on objects that don’t have a perfectly spherical interior structure, which is an assumption of most previous models.
The puzzling, fascinating surface of Jupiter’s icy moon Europa looms large in this newly-reprocessed color view, made from images taken by NASA’s Galileo spacecraft in the late 1990s. This is the color view of Europa from Galileo that shows the largest portion of the moon’s surface at the highest resolution. NASA/JPL-Caltech/SETI Institute Body tides refer to the deformations experienced by celestial bodies when they gravitationally interact with other objects. Think of how the powerful gravity of Jupiter tugs on its moon Europa. Because Europa’s orbit isn’t circular, the crushing squeeze of Jupiter’s gravity on the moon varies as it travels along its orbit. When Europa is at its closest to Jupiter, the planet’s gravity is felt the most. The energy of this deformation is what heats up Europa’s interior, allowing an ocean of liquid water to exist beneath the moon’s icy surface.
“The same is true for Saturn’s moon Enceladus.” says co-author Alexander Berne of CalTech in Pasadena and an affiliate at NASA’s Jet Propulsion Laboratory in Southern California. “Enceladus has an ice shell that is expected to be much more non-spherically symmetric than that of Europa.”
The body tides experienced by celestial bodies can affect how the worlds evolve over time and, in cases like Europa and Enceladus, their potential habitability for life as we know it. The new study provides a means to more accurately estimate how tidal forces affect planetary interiors.
In this movie Europa is seen in a cutaway view through two cycles of its 3.5 day orbit about the giant planet Jupiter. Like Earth, Europa is thought to have an iron core, a rocky mantle and a surface ocean of salty water. Unlike on Earth, however, this ocean is deep enough to cover the whole moon, and being far from the sun, the ocean surface is globally frozen over. Europa’s orbit is eccentric, which means as it travels around Jupiter, large tides, raised by Jupiter, rise and fall. Jupiter’s position relative to Europa is also seen to librate, or wobble, with the same period. This tidal kneading causes frictional heating within Europa, much in the same way a paper clip bent back and forth can get hot to the touch, as illustrated by the red glow in the interior of Europa’s rocky mantle and in the lower, warmer part of its ice shell. This tidal heating is what keeps Europa’s ocean liquid and could prove critical to the survival of simple organisms within the ocean, if they exist. The giant planet Jupiter is now shown to be rotating from west to east, though more slowly than its actual rate. NASA/JPL-Caltech The paper also discusses how the results of the study could help scientists interpret observations made by missions to a variety of different worlds, ranging from Mercury to the Moon to the outer planets of our solar system.
The study, “A Spectral Method to Compute the Tides of Laterally Heterogeneous Bodies,” was published in The Planetary Science Journal.
For more information on NASA’s Astrobiology Program, visit:
https://science.nasa.gov/astrobiology
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Karen Fox / Molly Wasser
Headquarters, Washington
202-358-1600
karen.c.fox@nasa.gov / molly.l.wasser@nasa.gov
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Last Updated Nov 07, 2024 Related Terms
Astrobiology View the full article
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By NASA
On Nov. 3, 1994, space shuttle Atlantis took to the skies on its 13th trip into space. During the 11-day mission, the STS-66 crew of Commander Donald R. McMonagle, Pilot Curtis L. Brown, Payload Commander Ellen Ochoa, and Mission Specialists Joseph R. Tanner, Scott E. Parazynski, and French astronaut Jean-François Clervoy representing the European Space Agency (ESA) operated the third Atmospheric Laboratory for Applications and Sciences (ATLAS-3), and deployed and retrieved the U.S.-German Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere-Shuttle Pallet Satellite (CRISTA-SPAS), as part of NASA’s Mission to Planet Earth. The remote sensing instruments studied the Sun’s energy output, the atmosphere’s chemical composition, and how these affect global ozone levels, adding to the knowledge gained during the ATLAS-1 and ATLAS-2 missions.
Left: Official photo of the STS-68 crew of Jean-François Clervoy, left, Scott E. Parazynski, Curtis L. Brown, Joseph R. Tanner, Donald R. McMonagle, and Ellen Ochoa. Middle: The STS-66 crew patch. Right: The ATLAS-3 payload patch.
In August 1993, NASA named Ochoa as the ATLAS-3 payload commander, and in January 1994, named the rest of the STS-66 crew. For McMonagle, selected as an astronaut in 1987, ATLAS-3 marked his third trip into space, having flown on STS-39 and STS-54. Brown, also from the class of 1987, previously flew on STS 47, while Ochoa, selected in 1990, flew as a mission specialist on STS-56, the ATLAS-2 mission. For Tanner, Parazynski, and Clervoy, all from the Class of 1992 – the French space agency CNES previously selected Clervoy as one of its astronauts in 1985 before he joined the ESA astronaut cadre in 1992 – STS-66 marked their first spaceflight.
Left: Schematic illustration of ATLAS-3 and its instruments. Right: Schematic illustration of CRISTA-SPAS retrievable satellite and its instruments.
The ATLAS-3 payload consisted of six instruments on a Spacelab pallet and one mounted on the payload bay sidewall. The pallet mounted instruments included Atmospheric Trace Molecule Spectroscopy (ATMOS), Millimeter-Wave Atmospheric Sounder (MAS), Active Cavity Radiometer Irradiance Monitor (ACRIM), Measurement of the Solar Constant (SOLCON), Solar Spectrum Measurement from 1,800 to 3,200 nanometers (SOLSCAN), and Solar Ultraviolet Spectral Irradiance Monitor (SUSIM).
The Shuttle Solar Backscatter Ultraviolet (SSBUV) instrument constituted the payload bay sidewall mounted experiment. While the instruments previously flew on the ATLAS-1 and ATLAS-2 missions, both those flights took place during the northern hemisphere spring. Data from the ATLAS-3’s mission in the fall complemented results from the earlier missions. The CRISTA-SPAS satellite included two instruments, the CRISTA and the Middle Atmosphere High Resolution Spectrograph Investigation (MAHRSI).
Left: Space shuttle Atlantis at Launch Pad 39B at NASA’s Kennedy Space Center in Florida. Middle: Liftoff of Atlantis on STS-66. Right: Atlantis rises into the sky.
Following its previous flight, STS-46 in August 1992, Atlantis spent one and a half years at the Rockwell plant in Palmdale, California, undergoing major modifications before arriving back at KSC on May 29, 1994. During the modification period, workers installed cables and wiring for a docking system for Atlantis to use during the first Shuttle-Mir docking mission in 1995 and equipment to allow it to fly Extended Duration Orbiter missions of two weeks or longer. Atlantis also underwent structural inspections and systems upgrades including improved nose wheel steering and a new reusable drag chute. Workers in KSC’s Orbiter Processing Facility installed the ATLAS-3 and CRISTA-SPAS payloads and rolled Atlantis over to the Vehicle Assembly Building on Oct. 4 for mating with its External Tank and Solid Rocket Boosters. Atlantis rolled out to Launch Pad 39B six days later. The six-person STS-66 crew traveled to KSC to participate in the Terminal Countdown Demonstration Test, essentially a dress rehearsal for the launch countdown, on Oct. 18.
They returned to KSC on Oct. 31, the same day the final countdown began. Following a smooth countdown leading to a planned 11:56 a.m. EST liftoff on Nov. 3, 1994, Atlantis took off three minutes late, the delay resulting from high winds at one of the Transatlantic Abort sites. The liftoff marked the third shuttle launch in 55 days, missing a record set in 1985 by one day. Eight and a half minutes later, Atlantis delivered its crew and payloads to space. Thirty minutes later, a firing of the shuttle’s Orbiter Maneuvering System (OMS) engines placed them in a 190-mile orbit inclined 57 degrees to the equator. The astronauts opened the payload bay doors, deploying the shuttle’s radiators, and removed their bulky launch and entry suits, stowing them for the remainder of the flight.
Left: Atlantis’ payload bay, showing the ATLAS-3 payload and the CRISTA-SPAS deployable satellite behind it. Middle: European Space Agency astronaut Jean-François Clervoy uses the shuttle’s Remote Manipulator System (RMS) to grapple the CRISTA-SPAS prior to its release. Right: Clervoy about to release CRISTA-SPAS from the RMS.
The astronauts began to convert their vehicle into a science platform, and that included breaking up into two teams to enable 24-hour-a-day operations. McMonagle, Ochoa, and Tanner made up the Red Team while Brown, Parazynski, and Clervoy made up the Blue Team. Within five hours of liftoff, the Blue Team began their sleep period while the Red Team started their first on orbit shift by activating the ATLAS-3 instruments, the CRISTA-SPAS deployable satellite, and the Remote Manipulator System (RMS) or robotic arm in the payload bay and some of the middeck experiments. The next day, Clervoy, operating the RMS, grappled CRISTA-SPAS, lifted it from its cradle in the payload bay, and while Atlantis flew over Germany, deployed it for its eight-day free flight. McMonagle fired Atlantis’ thrusters to separate from the satellite.
Left: Ellen Ochoa and Donald R. McMonagle on the shuttle’s flight deck. Middle: European Space Agency astronaut Jean-François Clervoy in the commander’s seat during the mission. Right: Scott E. Parazynski operates a protein crystallization experiment in the shuttle middeck.
Left: Joseph R. Tanner operates a protein crystallization experiment. Middle: Curtis L. Brown operates a microgravity acceleration measurement system. Right: Ellen Ochoa uses the shuttle’s Remote Manipulator System to grapple CRISTA-SPAS following its eight-day free flight.
For the next eight days, the two teams of astronauts continued work with the ATLAS instruments and several middeck and payload bay experiments such as protein crystal growth, measuring the shuttle microgravity acceleration environment, evaluating heat pipe performance, and a student experiment to study the Sun that complemented the ATLAS instruments. On November 12, the mission’s 10th day, the astronauts prepared to retrieve the CRISTA-SPAS satellite. For the retrieval, McMonagle and Brown used a novel rendezvous profile unlike previous ones used in the shuttle program. Instead of making the final approach from in front of the satellite, called the V-bar approach, Atlantis approached from below in the so-called R-bar approach. This is the profile Atlantis planned to use on its next mission, the first rendezvous and docking with the Mir space station. It not only saved fuel but also prevented contamination of the station’s delicate sensors and solar arrays. Once within 40 feet of CRISTA-SPAS, Ochoa reached out with the RMS, grappled the satellite, and then berthed it back in the payload bay.
A selection from the 6,000 STS-66 crew Earth observation photographs. Left: Deforestation in the Brazilian Amazon. Middle left: Hurricane Florence in the North Atlantic. Middle right: The Ganges River delta. Right: The Sakurajima Volcano in southern Japan.
As a Mission to Planet Earth, the STS-66 astronauts spent considerable time looking out the window, capturing 6,000 images of their home world. Their high inclination orbit enabled views of parts of the planet not seen during typical shuttle missions.
Left: The inflight STS-66 crew photo. Right: Donald R. McMonagle, left, and Curtis R. Brown prepare for Atlantis’ deorbit and reentry.
On flight day 11, with most of the onboard film exposed and consumables running low, the astronauts prepared for their return to Earth the following day. McMonagle and Brown tested Atlantis’ reaction control system thrusters and aerodynamic surfaces in preparation for deorbit and descent through the atmosphere, while the rest of the crew busied themselves with shutting down experiments and stowing away unneeded equipment.
Left: Atlantis makes a perfect touchdown at California’s Edwards Air Force Base. Middle: Atlantis deploys the first reusable space shuttle drag chute. Right: Mounted atop a Shuttle Carrier Aircraft, Atlantis departs Edwards for the cross-country trip to NASA’s Kennedy Space Center in Florida.
On Nov. 14, the astronauts closed Atlantis’ payload bay doors, donned their launch and entry suits, and strapped themselves into their seats for entry and landing. Tropical Storm Gordon near the KSC primary landing site forced a diversion to Edwards Air Force Base (AFB) in California. The crew fired Atlantis’ OMS engines to drop out of orbit. McMonagle piloted Atlantis to a smooth landing at Edwards, ending the 10-day 22-hour 34-minute flight, Atlantis’ longest flight up to that time. The crew had orbited the Earth 174 times. Workers at Edwards safed the vehicle and placed it atop a Shuttle Carrier Aircraft for the ferry flight back to KSC. The duo left Edwards on Nov. 21, and after stops at Kelly Field in San Antonio and Eglin AFB in the Florida panhandle, arrived at KSC the next day. Workers there began preparing Atlantis for its next flight, STS-71 in June 1995, the first Shuttle-Mir docking mission. Meanwhile, a Gulfstream jet flew the astronauts back to Ellington Field in Houston for reunions with their families. As it turned out, STS-66 flew Atlantis’ last solo flight until STS-125 in 2009, the final Hubble Servicing Mission. The 16 intervening flights, and the three that followed, all docked with either Mir or the International Space Station.
“The mission not only met all our expectations, but all our hopes and dreams as well,” said Mission Scientist Timothy L. Miller of NASA’s Marshall Space Flight Center in Huntsville, Alabama. “One of its high points was our ability to receive and process so much data in real time, enhancing our ability to carry out some new and unprecedented cooperative experiments.” McMonagle said of STS-66, “We are very proud of the mission we have just accomplished. If there’s any one thing we all have an interest in, it’s the health of our planet.”
Enjoy the crew narrate a video about the STS-66 mission.
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By NASA
3 min read
Buckle Up: NASA-Funded Study Explores Turbulence in Molecular Clouds
This image shows the distribution of density in a simulation of a turbulent molecular cloud. NASA/E. Scannapieco et al (2024) On an airplane, motions of the air on both small and large scales contribute to turbulence, which may result in a bumpy flight. Turbulence on a much larger scale is important to how stars form in giant molecular clouds that permeate the Milky Way.
In a new NASA-funded study in the journal Science Advances, scientists created simulations to explore how turbulence interacts with the density of the cloud. Lumps, or pockets of density, are the places where new stars will be born. Our Sun, for example, formed 4.6 billion years ago in a lumpy portion of a cloud that collapsed.
“We know that the main process that determines when and how quickly stars are made is turbulence, because it gives rise to the structures that create stars,” said Evan Scannapieco, professor of astrophysics at Arizona State University and lead author of the study. “Our study uncovers how those structures are formed.”
Giant molecular clouds are full of random, turbulent motions, which are caused by gravity, stirring by the galactic arms and winds, jets, and explosions from young stars. This turbulence is so strong that it creates shocks that drive the density changes in the cloud.
The simulations used dots called tracer particles to traverse a molecular cloud and travel along with the material. As the particles travel, they record the density of the part of the cloud they encounter, building up a history of how pockets of density change over time. The researchers, who also included Liubin Pan from Sun Yat Sen University in China, Marcus Brüggen from the University of Hamburg in Germany, and Ed Buie II from Vassar College in Poughkeepsie, New York, simulated eight scenarios, each with a different set of realistic cloud properties.
This animation shows the distribution of density in a simulation of a turbulent molecular cloud. The colors represent density, with dark blue indicating the least dense regions and red indicating the densest regions. Credit: NASA/E. Scannapieco et al (2024) The team found that the speeding up and slowing down of shocks plays an essential role in the path of the particles. Shocks slow down as they go into high-density gas and speed up as they go into low-density gas. This is akin to how an ocean wave strengthens when it hits shallow water by the shore.
When a particle hits a shock, the area around it becomes more dense. But because shocks slow down in dense regions, once lumps become dense enough, the turbulent motions can’t make them any denser. These lumpiest high-density regions are where stars are most likely to form.
While other studies have explored molecular cloud density structures, this simulation allows scientists to see how those structures form over time. This informs scientists’ understanding of how and where stars are likely to be born.
“Now we can understand better why those structures look the way they do because we’re able to track their histories,” said Scannapieco.
This image shows part of a simulation of a molecular cloud. The colors represent density, with dark blue indicating the least dense regions and red indicating the densest regions. Tracer particles, represented by black dots, traverse the simulated cloud. By examining how they interact with shocks and pockets of density, scientists can better understand the structures in molecular clouds that lead to star formation. NASA/E. Scannapieco et al (2024) NASA’s James Webb Space Telescope is exploring the structure of molecular clouds. It is also exploring the chemistry of molecular clouds, which depends on the history of the gas modeled in the simulations. New measurements like these will inform our understanding of star formation.
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By NASA
NASA/Don Pettit NASA astronaut Don Pettit fills a sphere of water with food coloring in this image from Oct. 20, 2024. Pettit calls experiments like these “science of opportunity” – moments of scientific exploration that spontaneously come to mind because of the unique experience of being on the International Space Station. During his previous missions, Pettit has contributed to advancements for human space exploration aboard the International Space Station resulting in several published scientific papers and breakthroughs.
See other inventive experiments Pettit has conducted.
Image credit: NASA/Don Pettit
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By NASA
4 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
Researchers think meltwater beneath Martian ice could support microbial life.
The white material seen within this Martian gully is believed to be dusty water ice. Scientists believe this kind of ice could be an excellent place to look for microbial life on Mars today. This image, showing part of a region called Dao Vallis, was captured by NASA’s Mars Reconnaissance Orbiter in 2009.NASA/JPL-Caltech/University of Arizona These holes, captured on Alaska’s Matanuska Glacier in 2012, are formed by cryoconite — dust particles that melt into the ice over time, eventually forming small pockets of water below the glacier’s surface. Scientists believe similar pockets of water could form within dusty water ice on Mars.Kimberly Casey CC BY-NC-SA 4.0 While actual evidence for life on Mars has never been found, a new NASA study proposes microbes could find a potential home beneath frozen water on the planet’s surface.
Through computer modeling, the study’s authors have shown that the amount of sunlight that can shine through water ice would be enough for photosynthesis to occur in shallow pools of meltwater below the surface of that ice. Similar pools of water that form within ice on Earth have been found to teem with life, including algae, fungi, and microscopic cyanobacteria, all of which derive energy from photosynthesis.
“If we’re trying to find life anywhere in the universe today, Martian ice exposures are probably one of the most accessible places we should be looking,” said the paper’s lead author, Aditya Khuller of NASA’s Jet Propulsion Laboratory in Southern California.
Mars has two kinds of ice: frozen water and frozen carbon dioxide. For their paper, published in Nature Communications Earth & Environment, Khuller and colleagues looked at water ice, large amounts of which formed from snow mixed with dust that fell on the surface during a series of Martian ice ages in the past million years. That ancient snow has since solidified into ice, still peppered with specks of dust.
Although dust particles may obscure light in deeper layers of the ice, they are key to explaining how subsurface pools of water could form within ice when exposed to the Sun: Dark dust absorbs more sunlight than the surrounding ice, potentially causing the ice to warm up and melt up to a few feet below the surface.
The white edges along these gullies in Mars’ Terra Sirenum are believed to be dusty water ice. Scientists think meltwater could form beneath the surface of this kind of ice, providing a place for possible photosynthesis. This is an enhanced-color image; the blue color would not actually be perceptible to the human eye.NASA/JPL-Caltech/University of Arizona Mars scientists are divided about whether ice can actually melt when exposed to the Martian surface. That’s due to the planet’s thin, dry atmosphere, where water ice is believed to sublimate — turn directly into gas — the way dry ice does on Earth. But the atmospheric effects that make melting difficult on the Martian surface wouldn’t apply below the surface of a dusty snowpack or glacier.
Thriving Microcosms
On Earth, dust within ice can create what are called cryoconite holes — small cavities that form in ice when particles of windblown dust (called cryoconite) land there, absorb sunlight, and melt farther into the ice each summer. Eventually, as these dust particles travel farther from the Sun’s rays, they stop sinking, but they still generate enough warmth to create a pocket of meltwater around them. The pockets can nourish a thriving ecosystem for simple lifeforms..
“This is a common phenomenon on Earth,” said co-author Phil Christensen of Arizona State University in Tempe, referring to ice melting from within. “Dense snow and ice can melt from the inside out, letting in sunlight that warms it like a greenhouse, rather than melting from the top down.”
Christensen has studied ice on Mars for decades. He leads operations for a heat-sensitive camera called THEMIS (Thermal Emission Imaging System) aboard NASA’s 2001 Mars Odyssey orbiter. In past research, Christensen and Gary Clow of the University of Colorado Boulder used modeling to demonstrate how liquid water could form within dusty snowpack on the Red Planet. That work, in turn, provided a foundation for the new paper focused on whether photosynthesis could be possible on Mars.
In 2021, Christensen and Khuller co-authored a paper on the discovery of dusty water ice exposed within gullies on Mars, proposing that many Martian gullies form by erosion caused by the ice melting to form liquid water.
This new paper suggests that dusty ice lets in enough light for photosynthesis to occur as deep as 9 feet (3 meters) below the surface. In this scenario, the upper layers of ice prevent the shallow subsurface pools of water from evaporating while also providing protection from harmful radiation. That’s important, because unlike Earth, Mars lacks a protective magnetic field to shield it from both the Sun and radioactive cosmic ray particles zipping around space.
The study authors say the water ice that would be most likely to form subsurface pools would exist in Mars’ tropics, between 30 degrees and 60 degrees latitude, in both the northern and southern hemispheres.
Khuller next hopes to re-create some of Mars’ dusty ice in a lab to study it up close. Meanwhile, he and other scientists are beginning to map out the most likely spots on Mars to look for shallow meltwater — locations that could be scientific targets for possible human and robotic missions in the future.
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Andrew Good
Jet Propulsion Laboratory, Pasadena, Calif.
818-393-2433
andrew.c.good@jpl.nasa.gov
Karen Fox / Molly Wasser
NASA Headquarters, Washington
202-358-1600
karen.c.fox@nasa.gov / molly.l.wasser@nasa.gov
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Last Updated Oct 17, 2024 Related Terms
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