123-462: This is a list of named geological features on Europa , a moon of the planet Jupiter . Craters and lineae are listed on separate pages: list of craters on Europa and list of lineae on Europa . Cavi are irregular steep-sided depressions that do not seem to be impact craters. On Europa, regions of chaotic terrain are named after places in Celtic mythology . A flexus is a low, curved ridge with
246-716: A 20×-magnification refracting telescope at the University of Padua , but the low resolution could not separate the two objects. The following night, he saw Io and Europa for the first time as separate bodies. The moon is the namesake of Europa , in Greek mythology the daughter of the Phoenician king of Tyre . Like all the Galilean satellites, Europa is named after a lover of Zeus , the Greek counterpart of Jupiter . Europa
369-625: A heat shield for an atmospheric probe did not yet exist, and facilities to test one under the conditions found on Jupiter would not be available until 1980. NASA management designated the Jet Propulsion Laboratory (JPL) as the lead center for the Jupiter Orbiter Probe (JOP) project. The JOP would be the fifth spacecraft to visit Jupiter, but the first to orbit it, and the probe would be the first to enter its atmosphere. An important decision made at this time
492-425: A non-synchronous rotation has been proposed: Europa spins faster than it orbits, or at least did so in the past. This suggests an asymmetry in internal mass distribution and that a layer of subsurface liquid separates the icy crust from the rocky interior. The slight eccentricity of Europa's orbit, maintained by gravitational disturbances from the other Galileans, causes Europa's sub-Jovian point to oscillate around
615-468: A 250 mm (9.8 in) aperture. Both the UVS and EUV instruments used a ruled grating to disperse light for spectral analysis. Light then passed through an exit slit into photomultiplier tubes that produced pulses of electrons, which were counted and the results sent to Earth. The UVS was mounted on Galileo 's scan platform. The EUV was mounted on the spun section. As Galileo rotated, EUV observed
738-424: A 5-meter long (16 ft) boom, carried 7.8 kilograms (17 lb) of Pu . Each RTG contained 18 separate heat source modules, and each module encased four pellets of plutonium(IV) oxide , a ceramic material resistant to fracturing. The plutonium was enriched to about 83.5 percent plutonium-238. The modules were designed to survive a range of potential accidents: launch vehicle explosion or fire, re-entry into
861-492: A Europa lander in 2011, along with concepts for a Europa flyby ( Europa Clipper ), and a Europa orbiter. The orbiter element option concentrates on the "ocean" science, while the multiple-flyby element ( Clipper ) concentrates on the chemistry and energy science. On 13 January 2014, the House Appropriations Committee announced a new bipartisan bill that includes $ 80 million in funding to continue
984-503: A broader color detection band than the vidicons of Voyager . The SSI was an 800-by-800-pixel charge-coupled device (CCD) camera. The optical portion of the camera was a modified flight spare of the Voyager narrow-angle camera; a Cassegrain telescope . The CCD had radiation shielding a 10 mm (0.4 in) thick layer of tantalum surrounding the CCD except where the light enters
1107-420: A central band of lighter material. The most likely hypothesis is that the lineae on Europa were produced by a series of eruptions of warm ice as Europa's crust slowly spreads open to expose warmer layers beneath. The effect would have been similar to that seen on Earth's oceanic ridges . These various fractures are thought to have been caused in large part by the tidal flexing exerted by Jupiter. Because Europa
1230-431: A faulty main engine controller that forced a postponement to October 17, and then by inclement weather, which necessitated a postponement to the following day, but this was not a concern since the launch window extended until November 21. Atlantis finally lifted off at 16:53:40 UTC on October 18, and went into a 343-kilometer (213 mi) orbit. Galileo was successfully deployed at 00:15 UTC on October 19. Following
1353-442: A few kilometers thick. However, most planetary scientists conclude that this model considers only those topmost layers of Europa's crust that behave elastically when affected by Jupiter's tides. One example is flexure analysis, in which Europa's crust is modeled as a plane or sphere weighted and flexed by a heavy load. Models such as this suggest the outer elastic portion of the ice crust could be as thin as 200 metres (660 ft). If
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#17327977155711476-560: A fixed axis or by maintaining a fixed orientation with reference to the Sun and a star. Galileo did both. One section of the spacecraft rotated at 3 revolutions per minute, keeping Galileo stable and holding six instruments that gathered data from many different directions, including the fields and particles instruments. Galileo was intentionally destroyed in Jupiter's atmosphere on September 21, 2003. The next orbiter to be sent to Jupiter
1599-699: A frozen sea. An alternative hypothesis suggests that lenticulae are actually small areas of chaos and that the claimed pits, spots and domes are artefacts resulting from the over-interpretation of early, low-resolution Galileo images. The implication is that the ice is too thin to support the convective diapir model of feature formation. In November 2011, a team of researchers, including researchers at University of Texas at Austin , presented evidence suggesting that many " chaos terrain " features on Europa sit atop vast lakes of liquid water. These lakes would be entirely encased in Europa's icy outer shell and distinct from
1722-443: A future lander. The Europa Clipper would not orbit Europa, but instead orbit Jupiter and conduct 45 low-altitude flybys of Europa during its envisioned mission. The probe would carry an ice-penetrating radar, short-wave infrared spectrometer, topographical imager, and an ion- and neutral-mass spectrometer. The mission was launched on 14 October 2024 aboard a Falcon Heavy . Conjectures regarding extraterrestrial life have ensured
1845-447: A height of 190 km (120 mi) above the surface of Europa. Molecular oxygen is the densest component of the atmosphere because it has a long lifetime; after returning to the surface, it does not stick (freeze) like a water or hydrogen peroxide molecule but rather desorbs from the surface and starts another ballistic arc. Molecular hydrogen never reaches the surface, as it is light enough to escape Europa's surface gravity. Europa
1968-554: A high profile for Europa and have led to steady lobbying for future missions. The aims of these missions have ranged from examining Europa's chemical composition to searching for extraterrestrial life in its hypothesized subsurface oceans. Robotic missions to Europa need to endure the high-radiation environment around Jupiter. Because it is deeply embedded within Jupiter's magnetosphere , Europa receives about 5.40 Sv of radiation per day. Galileo (spacecraft) Galileo
2091-635: A high-energy particle detector; and a detector of cosmic and Jovian dust . It also carried the Heavy Ion Counter, an engineering experiment to assess the potentially hazardous charged particle environments the spacecraft flew through, and an extreme ultraviolet detector associated with the UV spectrometer on the scan platform. The despun section's instruments included the camera system; the near infrared mapping spectrometer to make multi-spectral images for atmospheric and moon surface chemical analysis;
2214-527: A liquid ocean thought to exist farther down beneath the ice shell. Full confirmation of the lakes' existence will require a space mission designed to probe the ice shell either physically or indirectly, e.g. using radar. Chaos features may also be a result of increased melting of the ice shell and deposition of marine ice at low latitudes as a result of heterogeneous heating. Work published by researchers from Williams College suggests that chaos terrain may represent sites where impacting comets penetrated through
2337-440: A mean position. As Europa comes slightly nearer to Jupiter, Jupiter's gravitational attraction increases, causing Europa to elongate towards and away from it. As Europa moves slightly away from Jupiter, Jupiter's gravitational force decreases, causing Europa to relax back into a more spherical shape, and creating tides in its ocean. The orbital eccentricity of Europa is continuously pumped by its mean-motion resonance with Io. Thus,
2460-413: A narrow ribbon of space perpendicular to the spin axis. The two instruments combined weighed about 9.7 kg (21 lb) and used 5.9 watts of power. The PPR had seven radiometry bands. One of these used no filters and observed all incoming radiation, both solar and thermal. Another band allowed only solar radiation through. The difference between the solar-plus-thermal and the solar-only channels gave
2583-544: A part frozen as its crust and a part as a liquid ocean underneath the ice. Recent magnetic-field data from the Galileo orbiter showed that Europa has an induced magnetic field through interaction with Jupiter's, which suggests the presence of a subsurface conductive layer. This layer is likely to be a salty liquid-water ocean. Portions of the crust are estimated to have undergone a rotation of nearly 80°, nearly flipping over (see true polar wander ), which would be unlikely if
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#17327977155712706-510: A region where the subsurface ocean has melted through the icy crust. This interpretation is controversial. Most geologists who have studied Europa favor what is commonly called the "thick ice" model, in which the ocean has rarely, if ever, directly interacted with the present surface. The best evidence for the thick-ice model is a study of Europa's large craters. The largest impact structures are surrounded by concentric rings and appear to be filled with relatively flat, fresh ice; based on this and on
2829-503: A result of the moon's particle venting, the atmosphere requires continuous replenishment. Europa also contains a small magnetosphere (approximately 25% of Ganymede's). However, this magnetosphere varies in size as Europa orbits through Jupiter's magnetic field. This confirms that a conductive element, such as a large ocean, likely lies below its icy surface. As multiple studies have been conducted over Europa's atmosphere, several findings conclude that not all oxygen molecules are released into
2952-605: A scalloped pattern. Europan flexūs are named after the places visited by Europa during her journey with Zeus the bull. Fossae are named after ancient Celtic ancient stone rows. These impact structures are named after important locations in ancient history . Europan maculae (dark spots) are named after locations in Greek mythology , especially in the legend of Cadmus and his search for his sister, Europa . Europan regiones (regions) are named after locations in Celtic mythology . Europa (moon) Europa / j ʊ ˈ r oʊ p ə / , or Jupiter II ,
3075-534: A series of filters, and, from there, measurements were performed by the detectors of the PPR. The PPR weighed 5.0 kg (11.0 lb) and consumed about 5 watts of power. The dust-detector subsystem (DDS) was used to measure the mass, electric charge, and velocity of incoming particles. The masses of dust particles that the DDS could detect go from 10 to 10 grams. The speed of these small particles could be measured over
3198-475: A single Earth day (24 hours). A Europan day is about 3.5 times as long as an Earth day. Europa's most striking surface features are a series of dark streaks crisscrossing the entire globe, called lineae (English: lines ). Close examination shows that the edges of Europa's crust on either side of the cracks have moved relative to each other. The larger bands are more than 20 km (12 mi) across, often with dark, diffuse outer edges, regular striations, and
3321-537: A study was published in the peer-reviewed scientific journal Geophysical Research Letters suggesting that the plumes may originate from water within the crust of Europa as opposed to its subsurface ocean. The study's model, using images from the Galileo space probe, proposed that a combination of freezing and pressurization may result in at least some of the cryovolcanic activity. The pressure generated by migrating briny water pockets would thus, eventually, burst through
3444-411: A subsurface ocean came from theoretical considerations of tidal heating (a consequence of Europa's slightly eccentric orbit and orbital resonance with the other Galilean moons). Galileo imaging team members argue for the existence of a subsurface ocean from analysis of Voyager and Galileo images. The most dramatic example is "chaos terrain", a common feature on Europa's surface that some interpret as
3567-723: A succession of space-probe flybys, the first occurring in the early 1970s. In September 2022, the Juno spacecraft flew within about 320 km (200 miles) of Europa for a more recent close-up view. Europa has the smoothest surface of any known solid object in the Solar System. The apparent youth and smoothness of the surface is due to a water ocean beneath the surface, which could conceivably harbor extraterrestrial life , although such life would most likely be that of single celled organisms and bacteria -like creatures. The predominant model suggests that heat from tidal flexing causes
3690-503: A tilt in the spin axis would cause more heat to be generated by tidal forces. Such additional heat would have allowed the ocean to remain liquid for a longer time. However, it has not yet been determined when this hypothesized shift in the spin axis might have occurred. Europa is slightly smaller than the Earth's moon . At just over 3,100 kilometres (1,900 mi) in diameter , it is the sixth-largest moon and fifteenth-largest object in
3813-489: A tilted axis at some point in time. If correct, this would explain many of Europa's features. Europa's immense network of crisscrossing cracks serves as a record of the stresses caused by massive tides in its global ocean. Europa's tilt could influence calculations of how much of its history is recorded in its frozen shell, how much heat is generated by tides in its ocean, and even how long the ocean has been liquid. Its ice layer must stretch to accommodate these changes. When there
List of geological features on Europa - Misplaced Pages Continue
3936-492: A weak magnetic moment , which is induced by the varying part of the Jovian magnetic field. The field strength at the magnetic equator (about 120 nT ) created by this magnetic moment is about one-sixth the strength of Ganymede's field and six times the value of Callisto's. The existence of the induced moment requires a layer of a highly electrically conductive material in Europa's interior. The most plausible candidate for this role
4059-560: Is a large subsurface ocean of liquid saltwater. Since the Voyager spacecraft flew past Europa in 1979, scientists have worked to understand the composition of the reddish-brown material that coats fractures and other geologically youthful features on Europa's surface. Spectrographic evidence suggests that the darker, reddish streaks and features on Europa's surface may be rich in salts such as magnesium sulfate , deposited by evaporating water that emerged from within. Sulfuric acid hydrate
4182-470: Is a mission to Ganymede launched on 14 April 2023, that will include two flybys of Europa. NASA's Europa Clipper was launched on 14 October 2024, with a complementary lander possible based on its findings. Europa, along with Jupiter's three other large moons, Io , Ganymede , and Callisto , was discovered by Galileo Galilei on 8 January 1610, and possibly independently by Simon Marius . On 7 January, Galileo had observed Io and Europa together using
4305-457: Is another possible explanation for the contaminant observed spectroscopically. In either case, because these materials are colorless or white when pure, some other material must also be present to account for the reddish color, and sulfur compounds are suspected. Another hypothesis for the colored regions is that they are composed of abiotic organic compounds collectively called tholins . The morphology of Europa's impact craters and ridges
4428-511: Is due to a lack of substantial energy for organisms to thrive off, unlike proposed hydrothermal vents on the subsurface ocean floor. The atmosphere of Europa can be categorized as thin and tenuous (often called an exosphere), primarily composed of oxygen and trace amounts of water vapor. However, this quantity of oxygen is produced in a non-biological manner. Given that Europa's surface is icy, and subsequently very cold; as solar ultraviolet radiation and charged particles (ions and electrons) from
4551-534: Is due to direct overhead sunlight near the equator causing the ice to sublime , forming vertical cracks. Although the imaging available from the Galileo orbiter does not have the resolution for confirmation, radar and thermal data are consistent with this speculation. The ionizing radiation level at Europa's surface is equivalent to a daily dose of about 5.4 Sv (540 rem ), an amount that would cause severe illness or death in human beings exposed for
4674-406: Is now counted as Jupiter's sixth satellite, though it is still referred to as Jupiter II . The adjectival form has stabilized as Europan . Europa orbits Jupiter in just over three and a half days, with an orbital radius of about 670,900 km. With an orbital eccentricity of only 0.009, the orbit itself is nearly circular, and the orbital inclination relative to Jupiter's equatorial plane
4797-401: Is one of the few moons in our solar system with a quantifiable atmosphere, along with Titan , Io , Triton , Ganymede and Callisto . Europa is also one of several moons in our solar system with very large quantities of ice (volatiles) , otherwise known as "icy moons". Europa is also considered to be geologically active due to the constant release of hydrogen-oxygen mixtures into space. As
4920-530: Is possible due to the subsurface ocean mechanically decoupling Europa's surface from its rocky mantle and the effects of Jupiter's gravity tugging on Europa's outer ice crust. Comparisons of Voyager and Galileo spacecraft photos serve to put an upper limit on this hypothetical slippage. A full revolution of the outer rigid shell relative to the interior of Europa takes at least 12,000 years. Studies of Voyager and Galileo images have revealed evidence of subduction on Europa's surface, suggesting that, just as
5043-405: Is small, at 0.470°. Like its fellow Galilean satellites , Europa is tidally locked to Jupiter, with one hemisphere of Europa constantly facing Jupiter. Because of this, there is a sub-Jovian point on Europa's surface, from which Jupiter would appear to hang directly overhead. Europa's prime meridian is a line passing through this point. Research suggests that tidal locking may not be full, as
List of geological features on Europa - Misplaced Pages Continue
5166-408: Is suggestive of fluidized material welling up from the fractures where pyrolysis and radiolysis take place. In order to generate colored tholins on Europa, there must be a source of materials (carbon, nitrogen, and water) and a source of energy to make the reactions occur. Impurities in the water ice crust of Europa are presumed both to emerge from the interior as cryovolcanic events that resurface
5289-474: Is the smallest of the four Galilean moons orbiting Jupiter , and the sixth-closest to the planet of all the 95 known moons of Jupiter . It is also the sixth-largest moon in the Solar System . Europa was discovered independently by Simon Marius and Galileo Galilei and was named (by Marius) after Europa , the Phoenician mother of King Minos of Crete and lover of Zeus (the Greek equivalent of
5412-459: Is tidally locked to Jupiter, and therefore always maintains approximately the same orientation towards Jupiter, the stress patterns should form a distinctive and predictable pattern. However, only the youngest of Europa's fractures conform to the predicted pattern; other fractures appear to occur at increasingly different orientations the older they are. This could be explained if Europa's surface rotates slightly faster than its interior, an effect that
5535-426: Is too low to hold an atmosphere substantial enough for those features. Europa's gravity is approximately 13% of Earth's. The temperature on Europa varies from −160 °C at the equator, to −220 °C at either of its poles. Europa's subsurface ocean is thought to be significantly warmer however. It is hypothesized that because of radioactive and tidal heating (as mentioned in the sections above), there are points in
5658-443: Is too much stress, it cracks. A tilt in Europa's axis could suggest that its cracks may be much more recent than previously thought. The reason for this is that the direction of the spin pole may change by as much as a few degrees per day, completing one precession period over several months. A tilt could also affect estimates of the age of Europa's ocean. Tidal forces are thought to generate the heat that keeps Europa's ocean liquid, and
5781-584: The Galileo space probe, which orbited Jupiter from 1995 to 2003. Such plume activity could help researchers in a search for life from the subsurface Europan ocean without having to land on the moon. In March 2024, astronomers reported that the surface of Europa may have much less oxygen than previously inferred. The Galileo mission, launched in 1989, provides the bulk of current data on Europa. No spacecraft has yet landed on Europa, although there have been several proposed exploration missions. The European Space Agency 's Jupiter Icy Moon Explorer (JUICE)
5904-523: The 6502 that was being built into the Apple II desktop computer at that time. The Galileo Attitude and Articulation Control System (AACSE) was controlled by two Itek Advanced Technology Airborne Computers (ATAC), built using radiation-hardened 2901s . The AACSE could be reprogrammed in flight by sending the new program through the Command and Data Subsystem. The attitude control system software
6027-424: The Galileo space probe, which orbited Jupiter between 1995 and 2003. Galileo flew by Europa in 1997 within 206 km (128 mi) of the moon's surface and the researchers suggest it may have flown through a water plume. Such plume activity could help researchers in a search for life from the subsurface Europan ocean without having to land on the moon. The tidal forces are about 1,000 times stronger than
6150-426: The Solar System . Though by a wide margin the least massive of the Galilean satellites, it is nonetheless more massive than all known moons in the Solar System smaller than itself combined. Its bulk density suggests that it is similar in composition to terrestrial planets , being primarily composed of silicate rock . It is estimated that Europa has an outer layer of water around 100 km (62 mi) thick –
6273-446: The tidal flexing kneads Europa's interior and gives it a source of heat, possibly allowing its ocean to stay liquid while driving subsurface geological processes. The ultimate source of this energy is Jupiter's rotation, which is tapped by Io through the tides it raises on Jupiter and is transferred to Europa and Ganymede by the orbital resonance. Analysis of the unique cracks lining Europa yielded evidence that it likely spun around
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#17327977155716396-462: The EUV shared a communications link and, therefore, had to share observing time. The HIC weighed 8.0 kg (17.6 lb) and used an average of 2.8 watts of power. The magnetometer (MAG) used two sets of three sensors. The three sensors allowed the three orthogonal components of the magnetic field section to be measured. One set was located at the end of the magnetometer boom and, in that position,
6519-631: The Europa mission concept studies. In July 2013 an updated concept for a flyby Europa mission called Europa Clipper was presented by the Jet Propulsion Laboratory (JPL) and the Applied Physics Laboratory (APL). In May 2015, NASA announced that it had accepted development of the Europa Clipper mission, and revealed the instruments it would use. The aim of Europa Clipper is to explore Europa in order to investigate its habitability , and to aid in selecting sites for
6642-495: The IUS burn, the Galileo spacecraft adopted its configuration for solo flight, and separated from the IUS at 01:06:53 UTC on October 19. The launch was perfect, and Galileo was soon headed towards Venus at over 14,000 km/h (9,000 mph). Atlantis returned to Earth safely on October 23. The CDH subsystem was actively redundant, with two parallel data system buses running at all times. Each data system bus (a.k.a. string)
6765-966: The JPL in Pasadena, California , on the first leg of its journey, a road trip to the Kennedy Space Center in Florida . Due to the Space Shuttle Challenger disaster , the May launch date could not be met. The mission was rescheduled to October 12, 1989. The Galileo spacecraft would be launched by the STS-34 mission in the Space Shuttle Atlantis . As the launch date of Galileo neared, anti-nuclear groups , concerned over what they perceived as an unacceptable risk to
6888-452: The Jovian magnetospheric environment collide with Europa's surface, water vapor is created and instantaneously separated into oxygen and hydrogen constituents. As it continues to move, the hydrogen is light enough to pass through the surface gravity of the atmosphere leaving behind only oxygen. The surface-bounded atmosphere forms through radiolysis, the dissociation of molecules through radiation. This accumulated oxygen atmosphere can get to
7011-536: The Jupiter flybys of Pioneer 10 and 11 in 1973 and 1974, respectively. The first closeup photos were of low resolution compared to later missions. The two Voyager probes traveled through the Jovian system in 1979, providing more-detailed images of Europa's icy surface. The images caused many scientists to speculate about the possibility of a liquid ocean underneath. Starting in 1995, the Galileo space probe orbited Jupiter for eight years, until 2003, and provided
7134-578: The Mariner and Voyager projects, became the first project manager. He solicited suggestions for a more inspirational name for the project, and the most votes went to "Galileo" after Galileo Galilei , the first person to view Jupiter through a telescope. His 1610 discovery of what is now known as the Galilean moons orbiting Jupiter was important evidence of the Copernican model of the solar system. It
7257-498: The Moon's effect on Earth . The only other moon in the Solar System exhibiting water vapor plumes is Enceladus . The estimated eruption rate at Europa is about 7000 kg/s compared to about 200 kg/s for the plumes of Enceladus. If confirmed, it would open the possibility of a flyby through the plume and obtain a sample to analyze in situ without having to use a lander and drill through kilometres of ice. In November 2020,
7380-478: The Roman god Jupiter ). Slightly smaller than Earth's Moon , Europa is made of silicate rock and has a water-ice crust and probably an iron–nickel core. It has a very thin atmosphere, composed primarily of oxygen. Its geologically young white- beige surface is striated by light tan cracks and streaks, with very few impact craters. In addition to Earth-bound telescope observations, Europa has been examined by
7503-507: The atmosphere followed by land or water impact, and post-impact situations. An outer covering of graphite provided protection against the structural, thermal, and eroding environments of a potential re-entry into Earth's atmosphere. Additional graphite components provided impact protection, while iridium cladding of the RTGs provided post-impact containment. The RTGs produced about 570 watts at launch. The power output initially decreased at
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#17327977155717626-626: The atmosphere. This unknown percentage of oxygen may be absorbed into the surface and sink into the subsurface. Because the surface may interact with the subsurface ocean (considering the geological discussion above), this molecular oxygen may make its way to the ocean, where it could aid in biological processes. One estimate suggests that, given the turnover rate inferred from the apparent ~0.5 Gyr maximum age of Europa's surface ice, subduction of radiolytically generated oxidizing species might well lead to oceanic free oxygen concentrations that are comparable to those in terrestrial deep oceans. Through
7749-568: The body, and to accumulate from space as interplanetary dust. Tholins bring important astrobiological implications, as they may play a role in prebiotic chemistry and abiogenesis . The presence of sodium chloride in the internal ocean has been suggested by a 450 nm absorption feature, characteristic of irradiated NaCl crystals, that has been spotted in HST observations of the chaos regions, presumed to be areas of recent subsurface upwelling. The subterranean ocean of Europa contains carbon and
7872-479: The calculated amount of heat generated by Europan tides, it is estimated that the outer crust of solid ice is approximately 10 to 30 km (6 to 20 mi) thick, including a ductile "warm ice" layer, which could mean that the liquid ocean underneath may be about 100 km (60 mi) deep. This leads to a volume of Europa's oceans of 3×10 m , between two or three times the volume of Earth's oceans. The thin-ice model suggests that Europa's ice shell may be only
7995-426: The cracks are analogous to ocean ridges, so plates of icy crust analogous to tectonic plates on Earth are recycled into the molten interior. This evidence of both crustal spreading at bands and convergence at other sites suggests that Europa may have active plate tectonics , similar to Earth. However, the physics driving these plate tectonics are not likely to resemble those driving terrestrial plate tectonics, as
8118-632: The crust, thereby creating these plumes. The hypothesis that cryovolcanism on Europa could be triggered by freezing and pressurization of liquid pockets in the icy crust was first proposed by Sarah Fagents at the University of Hawai'i at Mānoa, who in 2003, was the first to model and publish work on this process. A press release from NASA's Jet Propulsion Laboratory referencing the November 2020 study suggested that plumes sourced from migrating liquid pockets could potentially be less hospitable to life. This
8241-402: The depths of Europa's ocean that may be only slightly cooler than Earth's oceans. Studies have also concluded that Europa's ocean would have been rather acidic at first, with large concentrations of sulfate, calcium, and carbon dioxide. But over the course of 4.5 billion years, it became full of chloride , thus resembling our 1.94% chloride oceans on Earth. Exploration of Europa began with
8364-615: The domes formed when the plains were pushed up from below. One hypothesis states that these lenticulae were formed by diapirs of warm ice rising up through the colder ice of the outer crust, much like magma chambers in Earth's crust. The smooth, dark spots could be formed by meltwater released when the warm ice breaks through the surface. The rough, jumbled lenticulae (called regions of "chaos"; for example, Conamara Chaos ) would then be formed from many small fragments of crust, embedded in hummocky, dark material, appearing like icebergs in
8487-724: The energetic particle population at Jupiter as a function of position and time. These measurements helped determine how the particles got their energy and how they were transported through Jupiter's magnetosphere. The EPD weighed 10.5 kg (23 lb) and used 10.1 watts of power on average. The HIC was, in effect, a repackaged and updated version of some parts of the flight spare of the Voyager cosmic-ray system. The HIC detected heavy ions using stacks of single crystal silicon wafers. The HIC could measure heavy ions with energies as low as 6 MeV (1 pJ) and as high as 200 MeV (32 pJ) per nucleon. This range included all atomic substances between carbon and nickel . The HIC and
8610-508: The fields and particles instruments. Back on the ground, the mission operations team used software containing 650,000 lines of code in the orbit sequence design process; 1,615,000 lines in the telemetry interpretation; and 550,000 lines of code in navigation. All of the spacecraft components and spare parts received a minimum of 2,000 hours of testing. The spacecraft was expected to last for at least five years—long enough to reach Jupiter and perform its mission. On December 19, 1985, it departed
8733-535: The first spacecraft to orbit an outer planet. The Jet Propulsion Laboratory built the Galileo spacecraft and managed the Galileo program for NASA . West Germany's Messerschmitt-Bölkow-Blohm supplied the propulsion module. NASA's Ames Research Center managed the atmospheric probe, which was built by Hughes Aircraft Company . At launch, the orbiter and probe together had a mass of 2,562 kg (5,648 lb) and stood 6.15 m (20.2 ft) tall. Spacecraft are normally stabilized either by spinning around
8856-533: The following functions: The propulsion subsystem consisted of a 400 N (90 lbf) main engine and twelve 10 N (2.2 lbf) thrusters, together with propellant, storage and pressurizing tanks and associated plumbing. The 10 N thrusters were mounted in groups of six on two 2-meter (6.6 ft) booms. The fuel for the system was 925 kg (2,039 lb) of monomethylhydrazine and nitrogen tetroxide . Two separate tanks held another 7 kg (15 lb) of helium pressurant. The propulsion subsystem
8979-422: The following functions: The spacecraft was controlled by six RCA 1802 COSMAC microprocessor CPUs : four on the spun side and two on the despun side. Each CPU was clocked at about 1.6 MHz, and fabricated on sapphire ( silicon on sapphire ), which is a radiation-and static-hardened material ideal for spacecraft operation. This 8-bit microprocessor was the first low-power CMOS processor chip, similar to
9102-428: The forces resisting potential Earth-like plate motions in Europa's crust are significantly stronger than the forces that could drive them. Other features present on Europa are circular and elliptical lenticulae ( Latin for "freckles"). Many are domes, some are pits and some are smooth, dark spots. Others have a jumbled or rough texture. The dome tops look like pieces of the older plains around them, suggesting that
9225-405: The heat generated by the ice actually comes from the ice's crystalline structure (lattice) as a result of deformation, and not friction between the ice grains. The greater the deformation of the ice sheet, the more heat is generated. In addition to tidal heating, the interior of Europa could also be heated by the decay of radioactive material ( radiogenic heating ) within the rocky mantle. But
9348-698: The height of Mt. Everest., though recent observations and modeling suggest that typical Europan plumes may be much smaller. It has been suggested that if plumes exist, they are episodic and likely to appear when Europa is at its farthest point from Jupiter, in agreement with tidal force modeling predictions. Additional imaging evidence from the Hubble Space Telescope was presented in September 2016. In May 2018, astronomers provided supporting evidence of water plume activity on Europa, based on an updated critical analysis of data obtained from
9471-447: The highest of any moon. This indicates a young and active surface: based on estimates of the frequency of cometary bombardment that Europa experiences, the surface is about 20 to 180 million years old. There is no scientific consensus about the explanation for Europa's surface features. It has been postulated Europa's equator may be covered in icy spikes called penitentes , which may be up to 15 meters high. Their formation
9594-454: The ice crust and into an underlying ocean. The scientific consensus is that a layer of liquid water exists beneath Europa's surface, and that heat from tidal flexing allows the subsurface ocean to remain liquid. Europa's surface temperature averages about 110 K (−160 °C ; −260 °F ) at the equator and only 50 K (−220 °C; −370 °F) at the poles, keeping Europa's icy crust as hard as granite. The first hints of
9717-401: The ice shell of Europa is really only a few kilometers thick, this "thin ice" model would mean that regular contact of the liquid interior with the surface could occur through open ridges, causing the formation of areas of chaotic terrain. Large impacts going fully through the ice crust would also be a way that the subsurface ocean could be exposed. The Galileo orbiter found that Europa has
9840-502: The ice were solidly attached to the mantle. Europa probably contains a metallic iron core. Europa is the smoothest known object in the Solar System, lacking large-scale features such as mountains and craters. The prominent markings crisscrossing Europa appear to be mainly albedo features that emphasize low topography. There are few craters on Europa, because its surface is tectonically too active and therefore young. Its icy crust has an albedo (light reflectivity) of 0.64, one of
9963-433: The magnetic fields. The electric dipole antenna was mounted at the tip of the magnetometer boom. The search coil magnetic antennas were mounted on the high-gain antenna feed. Nearly simultaneous measurements of the electric and magnetic field spectrum allowed electrostatic waves to be distinguished from electromagnetic waves . The PWS weighed 7.1 kg (16 lb) and used an average of 9.8 watts. The atmospheric probe
10086-459: The mid-20th century. In much of the earlier astronomical literature, Europa is simply referred to by its Roman numeral designation as Jupiter II (a system also introduced by Galileo) or as the "second satellite of Jupiter". In 1892, the discovery of Amalthea , whose orbit lay closer to Jupiter than those of the Galilean moons, pushed Europa to the third position. The Voyager probes discovered three more inner satellites in 1979, so Europa
10209-432: The models and values observed are one hundred times higher than those that could be produced by radiogenic heating alone, thus implying that tidal heating has a leading role in Europa. The Hubble Space Telescope acquired an image of Europa in 2012 that was interpreted to be a plume of water vapour erupting from near its south pole. The image suggests the plume may be 200 km (120 mi) high, or more than 20 times
10332-418: The most detailed examination of the Galilean moons to date. It included the "Galileo Europa Mission" and "Galileo Millennium Mission", with numerous close flybys of Europa. In 2007, New Horizons imaged Europa, as it flew by the Jovian system while on its way to Pluto . In 2022, the Juno orbiter flew by Europa at a distance of 352 km (219 mi). In 2012, Jupiter Icy Moons Explorer (JUICE)
10455-589: The ocean flow could be 100 to thousands of times greater than the heat generated by the flexing of Europa's rocky core in response to the gravitational pull from Jupiter and the other moons circling that planet. Europa's seafloor could be heated by the moon's constant flexing, driving hydrothermal activity similar to undersea volcanoes in Earth's oceans. Experiments and ice modeling published in 2016, indicate that tidal flexing dissipation can generate one order of magnitude more heat in Europa's ice than scientists had previously assumed. Their results indicate that most of
10578-762: The ocean to remain liquid and drives ice movement similar to plate tectonics , absorbing chemicals from the surface into the ocean below. Sea salt from a subsurface ocean may be coating some geological features on Europa, suggesting that the ocean is interacting with the sea floor. This may be important in determining whether Europa could be habitable. In addition, the Hubble Space Telescope detected water vapor plumes similar to those observed on Saturn's moon Enceladus , which are thought to be caused by erupting cryogeysers . In May 2018, astronomers provided supporting evidence of water plume activity on Europa, based on an updated analysis of data obtained from
10701-444: The oceans and their interaction with the solid bottom and with the top ice crust. In late 2008, it was suggested Jupiter may keep Europa's oceans warm by generating large planetary tidal waves on Europa because of its small but non-zero obliquity. This generates so-called Rossby waves that travel quite slowly, at just a few kilometers per day, but can generate significant kinetic energy. For the current axial tilt estimate of 0.1 degree,
10824-468: The orbiter and probe together had a mass of 2,562 kg (5,648 lb) and stood 6.15 m (20.2 ft) tall. Spacecraft are normally stabilized either by spinning around a fixed axis or by maintaining a fixed orientation with reference the Sun and a star; Galileo did both. One section of the spacecraft rotated at 3 revolutions per minute , keeping Galileo stable and holding six instruments that gathered data from many different directions, including
10947-464: The outboard (11 m) set of sensors could measure magnetic field strengths in the range from ±32 to ±512 nT, while the inboard (6.7 m) set was active in the range from ±512 to ±16,384 nT. The MAG experiment weighed 7.0 kg (15.4 lb) and used 3.9 watts of power. The PLS used seven fields of view to collect charged particles for energy and mass analysis. These fields of view covered most angles from 0 to 180 degrees, fanning out from
11070-492: The process of neutral particles exchanging electrons with its charged particles. Since Europa's magnetic field rotates faster than its orbital velocity, these ions are left in the path of its magnetic field trajectory, forming a plasma. It has been hypothesized that these ions are responsible for the plasma within Jupiter's magnetosphere. On 4 March 2024, astronomers reported that the surface of Europa may have much less oxygen than previously inferred. The atmosphere of Europa
11193-413: The propulsion module and most of Galileo 's computers and control electronics. The sixteen instruments, weighing 118 kg (260 lb) altogether, included magnetometer sensors mounted on an 11 m (36 ft) boom to minimize interference from the spacecraft; a plasma instrument for detecting low-energy charged particles and a plasma-wave detector to study waves generated by the particles;
11316-403: The public's safety from the plutonium in the Galileo 's radioisotope thermoelectric generators (RTGs) and General Purpose Heat Source (GPHS) modules, sought a court injunction prohibiting Galileo 's launch. RTGs were necessary for deep space probes because they had to fly distances from the Sun that made the use of solar energy impractical. The launch was delayed twice more: by
11439-402: The range of 1 to 70 kilometers per second (0.6 to 43.5 mi/s). The instrument could measure impact rates from 1 particle per 115 days (10 megaseconds) to 100 particles per second. Such data was used to help determine dust origin and dynamics within the magnetosphere . The DDS weighed 4.2 kg (9.3 lb) and used an average of 5.4 watts of power. The energetic-particles detector (EPD)
11562-426: The rate of 0.6 watts per month and was 493 watts when Galileo arrived at Jupiter. The spacecraft had a large high-gain antenna which failed to deploy while in space, so the low-gain antenna was used instead, although at slower data transfer speeds. Scientific instruments to measure fields and particles were mounted on the spinning section of the spacecraft, together with the main antenna , power supply,
11685-400: The resonance from Rossby waves would contain 7.3 × 10 J of kinetic energy, which is two thousand times larger than that of the flow excited by the dominant tidal forces. Dissipation of this energy could be the principal heat source of Europa's ocean. Tidal flexing kneads Europa's interior and ice shell, which becomes a source of heat. Depending on the amount of tilt, the heat generated by
11808-469: The slow release of oxygen and hydrogen, a neutral torus around Europa's orbital plane is formed. This "neutral cloud" has been detected by both the Cassini and Galileo spacecraft, and has a greater content (number of atoms and molecules) than the neutral cloud surrounding Jupiter's inner moon Io. This torus was officially confirmed using Energetic Neutral Atom (ENA) imaging. Europa's torus ionizes through
11931-417: The spin axis. The rotation of the spacecraft carried each field of view through a full circle. The PLS measured particles in the energy range from 0.9 to 52,000 eV (0.14 to 8,300 aJ ). The PLS weighed 13.2 kg (29 lb) and used an average of 10.7 watts of power. An electric dipole antenna was used to study the electric fields of plasmas , while two search coil magnetic antennas studied
12054-486: The system. An eight-position filter wheel was used to obtain images at specific wavelengths. The images were then combined electronically on Earth to produce color images. The spectral response of the SSI ranged from about 400 to 1100 nm. The SSI weighed 29.7 kg (65 lb) and consumed, on average, 15 watts of power. The NIMS instrument was sensitive to 0.7-to-5.2- micrometer wavelength infrared light, overlapping
12177-493: The total thermal radiation emitted. The PPR also measured in five broadband channels that spanned the spectral range from 17 to 110 micrometers. The radiometer provided data on the temperatures of Jupiter's atmosphere and satellites. The design of the instrument was based on that of an instrument flown on the Pioneer Venus spacecraft. A 100 mm (4 in) aperture reflecting telescope collected light and directed it to
12300-425: The ultraviolet spectrometer to study gases; and the photopolarimeter-radiometer to measure radiant and reflected energy. The camera system was designed to obtain images of Jupiter's satellites at resolutions 20 to 1,000 times better than Voyager 's best, because Galileo flew closer to the planet and its inner moons, and because the more modern CCD sensor in Galileo 's camera was more sensitive and had
12423-403: The wavelength range of the SSI. NIMS used a 229 mm (9 in) aperture reflecting telescope. The spectrometer used a grating to disperse the light collected by the telescope. The dispersed spectrum of light was focused on detectors of indium , antimonide and silicon . NIMS weighed 18 kg (40 lb) and used 12 watts of power on average. The Cassegrain telescope of the UVS had
12546-418: Was Juno , which arrived on July 5, 2016. Jupiter is the largest planet in the Solar System , with more than twice the mass of all the other planets combined. Consideration of sending a probe to Jupiter began as early as 1959. NASA's Scientific Advisory Group (SAG) for Outer Solar System Missions considered the requirements for Jupiter orbiters and atmospheric probes. It noted that the technology to build
12669-670: Was Ganymede, the handsome son of King Tros, whom Jupiter, having taken the form of an eagle, transported to heaven on his back, as poets fabulously tell... I think, therefore, that I shall not have done amiss if the First is called by me Io, the Second Europa, the Third, on account of its majesty of light, Ganymede, the Fourth Callisto... The names fell out of favor for a considerable time and were not revived in general use until
12792-458: Was about 11 m (36 ft) from the spin axis of the spacecraft. The second set, designed to detect stronger fields, was 6.7 m (22 ft) from the spin axis. The boom was used to remove the MAG from the immediate vicinity of Galileo to minimize magnetic effects from the spacecraft. However, not all these effects could be eliminated by distancing the instrument. The rotation of the spacecraft
12915-560: Was also noted that the name was that of a spacecraft in the Star Trek television show. The new name was adopted in February 1978. The Jet Propulsion Laboratory built the Galileo spacecraft and managed the Galileo mission for NASA. West Germany 's Messerschmitt-Bölkow-Blohm supplied the propulsion module. NASA's Ames Research Center managed the atmospheric probe, which was built by Hughes Aircraft Company . At launch,
13038-517: Was an American robotic space probe that studied the planet Jupiter and its moons , as well as the asteroids Gaspra and Ida . Named after the Italian astronomer Galileo Galilei , it consisted of an orbiter and an entry probe. It was delivered into Earth orbit on October 18, 1989, by Space Shuttle Atlantis , during STS-34 . Galileo arrived at Jupiter on December 7, 1995, after gravitational assist flybys of Venus and Earth, and became
13161-507: Was built by Hughes Aircraft Company 's Space and Communications Group at its El Segundo, California plant. It weighed 339 kilograms (747 lb) and was 86 centimeters (34 in) high. Inside the probe's heat shield , the scientific instruments were protected from extreme heat and pressure during its high-speed journey into the Jovian atmosphere, entering at 48 kilometers per second (110,000 mph). Temperatures reached around 16,000 °C (29,000 °F). The ablative heat shield
13284-458: Was built up around a single 1802 microprocessor and 32K of RAM (for HLMs) or 16K of RAM (for LLMs). Two HLMs and two LLMs resided on the spun side while two LLMs were on the despun side. Thus, total memory capacity available to the CDH subsystem was 176K of RAM: 144K allocated to the spun side and 32K to the despun side. Each HLM was responsible for the following functions: Each LLM was responsible for
13407-404: Was composed of the same functional elements, consisting of multiplexers (MUX), high-level modules (HLM), low-level modules (LLM), power converters (PC), bulk memory (BUM), data management subsystem bulk memory (DBUM), timing chains (TC), phase locked loops (PLL), Golay coders (GC), hardware command decoders (HCD) and critical controllers (CRC). The CDH subsystem was responsible for maintaining
13530-476: Was courted by Zeus and became the queen of Crete . The naming scheme was suggested by Simon Marius, who attributed the proposal to Johannes Kepler : Jupiter is much blamed by the poets on account of his irregular loves. Three maidens are especially mentioned as having been clandestinely courted by Jupiter with success. Io, daughter of the River Inachus, Callisto of Lycaon, Europa of Agenor. Then there
13653-416: Was designed to measure the numbers and energies of ions and electrons whose energies exceeded about 20 keV (3.2 fJ). The EPD could also measure the direction of travel of such particles and, in the case of ions, could determine their composition (whether the ion is oxygen or sulfur , for example). The EPD used silicon solid-state detectors and a time-of-flight detector system to measure changes in
13776-439: Was determined with reference to the Sun and Canopus , which were monitored with two primary and four secondary sensors. There was also an inertial reference unit and an accelerometer . This allowed it to take high-resolution images, but the functionality came at a cost of increased weight. A Mariner weighed 722 kilograms (1,592 lb) compared to just 146 kilograms (322 lb) for a Pioneer. John R. Casani , who had headed
13899-490: Was developed and built by Messerschmitt-Bölkow-Blohm and provided by West Germany, the major international partner in Project Galileo . At the time, solar panels were not practical at Jupiter's distance from the Sun; the spacecraft would have needed a minimum of 65 square meters (700 sq ft) of panels. Chemical batteries would likewise be prohibitively large due to technological limitations. The solution
14022-492: Was first discovered in 1995 by astronomers D. T. Hall and collaborators using the Goddard High Resolution Spectrograph instrument of the Hubble Space Telescope . This observation was further supported in 1997 by the Galileo orbiter during its mission within the Jovian system. The Galileo orbiter performed three radio occultation events of Europa, where the probe's radio contact with Earth
14145-534: Was made of carbon phenolic . NASA built a special laboratory, the Giant Planet Facility, to simulate the heat load, which was similar to the convective and radiative heating experienced by an ICBM warhead reentering the atmosphere. The probe's electronics were powered by 13 lithium sulfur dioxide batteries manufactured by Honeywell 's Power Sources Center in Horsham, Pennsylvania . Each cell
14268-528: Was observed on the surface ice as a concentration of carbon dioxide within Tara Regio, a geologically recently resurfaced terrain. Europa receives thermal energy from tidal heating , which occurs through the tidal friction and tidal flexing processes caused by tidal acceleration : orbital and rotational energy are dissipated as heat in the core of the moon, the internal ocean, and the ice crust. Ocean tides are converted to heat by frictional losses in
14391-546: Was selected by the European Space Agency ( ESA ) as a planned mission. That mission includes two flybys of Europa, but is more focused on Ganymede . It was launched in 2023, and is expected to reach Jupiter in July 2031 after four gravity assists and eight years of travel. In 2011, a Europa mission was recommended by the U.S. Planetary Science Decadal Survey . In response, NASA commissioned concept studies of
14514-473: Was temporarily blocked by passing behind Europa. By analyzing the effects Europa's sparse atmosphere had on the radio signal just before and after the occultation, for a total of six events, a team of astronomers led by A. J. Kliore established the presence of an ionized layer in Europa's atmosphere. Despite the presence of a gas torus , Europa has no weather producing clouds. As a whole, Europa has no wind, precipitation, or presence of sky color as its gravity
14637-433: Was the size of a D battery so existing manufacturing tools could be used. They provided a nominal power output of about 7.2-ampere hours capacity at a minimal voltage of 28.05 volts. The probe included seven instruments for taking data on its plunge into Jupiter: In addition, the probe's heat shield contained instrumentation to measure ablation during descent. Lacking the fuel to escape Jupiter's gravity well, at
14760-408: Was to use a Mariner program spacecraft like that used for Voyager for the Jupiter orbiter, rather than a Pioneer. Pioneer was stabilized by spinning the spacecraft at 60 rpm , which gave a 360-degree view of the surroundings, and did not require an attitude control system. By contrast, Mariner had an attitude control system with three gyroscopes and two sets of six nitrogen jet thrusters. Attitude
14883-417: Was two radioisotope thermoelectric generators (RTGs) which powered the spacecraft through the radioactive decay of plutonium-238 . The heat emitted by this decay was converted into electricity through the solid-state Seebeck effect . This provided a reliable and long-lasting source of electricity unaffected by the cold environment and high-radiation fields in the Jovian system. Each GPHS-RTG , mounted on
15006-440: Was used to separate natural magnetic fields from engineering-induced fields. Another source of potential error in measurement came from the bending and twisting of the long magnetometer boom. To account for these motions, a calibration coil was mounted rigidly on the spacecraft to generate a reference magnetic field during calibrations. The magnetic field at the surface of the Earth has a strength of about 50,000 nT . At Jupiter,
15129-620: Was written in the HAL/S programming language, which was also used in the Space Shuttle program . Memory capacity provided by each BUM was 16K of RAM , while the DBUMs each provided 8K of RAM. There were two BUMs and two DBUMs in the CDH subsystem and they all resided on the spun side of the spacecraft. The BUMs and DBUMs provided storage for sequences and contain various buffers for telemetry data and interbus communication. Every HLM and LLM
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