67P/Churyumov–Gerasimenko

67P/Churyumov–Gerasimenko (abbreviated as 67P or 67P/C-G) is a Jupiter-family comet,[8] originally from the Kuiper belt,[9] with a current orbital period of 6.45 years,[1] a rotation period of approximately 12.4 hours[7] and a maximum velocity of 135,000 km/h (38 km/s; 84,000 mph).[10] Churyumov–Gerasimenko is approximately 4.3 by 4.1 km (2.7 by 2.5 mi) at its longest and widest dimensions.[11] It was first observed on photographic plates in 1969 by Soviet astronomers Klim Ivanovych Churyumov and Svetlana Ivanovna Gerasimenko, after whom it is named. It came to perihelion (closest approach to the Sun) on 13 August 2015.[2][12][13][14]

Churyumov–Gerasimenko was the destination of the European Space Agency's Rosetta mission, launched on 2 March 2004.[15][16][17] Rosetta rendezvoused with Churyumov–Gerasimenko on 6 August 2014[18][19] and entered orbit on 10 September 2014.[20] Rosetta's lander, Philae, landed on the comet's surface on 12 November 2014, becoming the first spacecraft to land on a comet nucleus.[21][22][23] On 30 September 2016, the Rosetta spacecraft ended its mission by landing on the comet in its Ma'at region.[24][25]

67P/Churyumov–Gerasimenko
Comet 67P on 19 September 2014 NavCam mosaic
Greyscale photograph of Comet Churyumov–Gerasimenko taken by the Rosetta spacecraft
Discovery
Discovered byKlim Ivanovich Churyumov
Svetlana Ivanovna Gerasimenko
Discovery siteAlma-Ata, Kazakh SSR, Soviet Union
Kiev, Ukrainian SSR, Soviet Union
Discovery date20 September 1969
Designations
1969 R1, 1969 IV, 1969h, 1975 P1, 1976 VII, 1975i, 1982 VIII, 1982f, 1989 VI, 1988i[1]
Orbital characteristics[1]
Epoch 10 August 2014 (JD 2456879.5)
Aphelion5.6829 AU
     (850,150,000 km; 528,260,000 mi)
Perihelion1.2432 AU
     (185,980,000 km; 115,560,000 mi)
3.4630 AU
     (518,060,000 km; 321,910,000 mi)
Eccentricity0.64102
6.44 yr
303.71°
Inclination7.0405°
50.147°
13 August 2015[2]
12.780°
Physical characteristics
Dimensions
  • Large lobe: 4.1 km × 3.3 km × 1.8 km
    (2.5 mi × 2.1 mi × 1.1 mi)[3]
  • Small lobe: 2.6 km × 2.3 km × 1.8 km
    (1.6 mi × 1.4 mi × 1.1 mi)[3]
Volume18.7 km3 (4.5 cu mi)[4]
Mass(9.982±0.003)×1012 kg[4]
Mean density
0.533 ± 0.006 g/cm3 [4][5]
     (0.01926 ± 0.00022 lb/cu in)
est. 1 m/s (3 ft/s)[6]
12.4043±0.0007 h[7]
52°[3]
North pole right ascension
69.3°[3]
North pole declination
64.1°[3]
Albedo0.06[3]
Surface temp. min mean max
Kelvin 180 230
Celsius −93 −43
Fahrenheit −135 −45

Discovery

Churyumov–Gerasimenko was discovered in 1969 by Klim Ivanovich Churyumov of the Kiev University's Astronomical Observatory,[26] who examined a photograph that had been exposed for comet Comas Solà by Svetlana Ivanovna Gerasimenko on 11 September 1969 at the Alma-Ata Astrophysical Institute, near Alma-Ata (now Almaty), the then-capital city of Kazakh Soviet Socialist Republic, Soviet Union. Churyumov found a cometary object near the edge of the plate, but assumed that this was comet Comas Solà.[27]

After returning to his home institute in Kiev, Churyumov examined all the photographic plates more closely. On 22 October, about a month after the photograph was taken, he discovered that the object could not be Comas Solà, because it was about 1.8 degrees off the expected position. Further scrutiny produced a faint image of Comas Solà at its expected position on the plate, thus proving the other object to be a different body.[27]

Shape

Comet 67P-Churyumov-Gerasimenko.stl
3D model of 67P by ESA (click to rotate)

The comet consists of two lobes connected by a narrower neck, with the larger lobe measuring about 4.1 km × 3.3 km × 1.8 km (2.5 mi × 2.1 mi × 1.1 mi) and the smaller one about 2.6 km × 2.3 km × 1.8 km (1.6 mi × 1.4 mi × 1.1 mi).[3] With each orbit the comet loses matter, as gas and dust are evaporated away by the sun. It is estimated that currently a layer with an average thickness of about 1 ± 0.5 m (3.3 ± 1.6 ft) is lost per orbit.[28] The comet has a mass of approximately 10 billion tonnes.[4]

The two-lobe shape of the comet is the result of a gentle, low-velocity collision of two objects. The "terraces", layers of the interior of the comet that have been exposed by partial stripping of outer layers during its existence, are oriented in different directions in the two lobes, indicating that two objects fused to form Churyumov–Gerasimenko.[29][30]

Surface

67P Churyumov-Gerasimenko surface
Dust and cosmic rays on the surface of the comet in 2016, with stars moving in the background

There are 26 distinct regions on Churyumov–Gerasimenko, with each named after an Egyptian deity; regions on the large lobe are named after gods, whereas those on the small lobe are named after goddesses. 19 regions were defined in the northern hemisphere prior to equinox.[31][32] Later, when the southern hemisphere became illuminated, seven more regions were identified using the same naming convention.[33][34]

Region Terrain Region Terrain Region Terrain
Ma'at Dust covered Ash Dust covered Babi Dust covered
Seth Pitted and brittle material Hatmehit Large-scale depression Nut Large-scale depression
Aten Large-scale depression Hapi Smooth Imhotep Smooth
Anubis Smooth Maftet Rock-like Bastet Rock-like
Serqet Rock-like Hathor Rock-like Anuket Rock-like
Khepry Rock-like Aker Rock-like Atum Rock-like
Apis Rock-like Khonsu Rock-like Bes Rock-like
Anhur Rock-like, rather friable Geb Rock-like Sobek Rock-like
Neith Rock-like Wosret Rock-like

Gates

Features described as gates, twin prominences on the surface so named for their appearance, have received names by the Rosetta Science Working Team. They are named after deceased members of the Rosetta team.[35]

Name Named after
C. Alexander Gate Claudia Alexander
A. Coradini Gate Angioletta Coradini

Surface changes

During Rosetta's lifetime, many changes were observed on the comet's surface, particularly when the comet was close to perihelion.[36][37][38] These changes included evolving patterns of circular shapes in smooth terrains that at some point grew in size by a few meters per day.[39][40] A fracture in the neck region was also observed to grow in size; boulders tens of meters wide were displaced, sometimes travelling more than 100 meters; and patches of the ground were removed to expose new features. A number of collapsing cliffs have also been observed. One notable example in December 2015 was captured by Rosetta's NAVCAM as a bright patch of light shining from the comet. Rosetta scientists determined that a large cliff had collapsed, making it the first landslide on a comet known to be associated with an outburst of activity.[41][42]

Orbit and rotation

Comet 67P orbit perihelion 2015
The orbit of 67P/Churyumov–Gerasimenko moves from just inside the orbit of Mars to just outside the orbit of Jupiter, seen here at perihelion in August 2015.
NavCam Comet 67P animation 20140806 (cropped)
This animation consists of 86 images acquired by Rosetta's NavCam as it approached 67P in August 2014.

Like the other comets of the Jupiter family, Churyumov–Gerasimenko probably originated in the Kuiper belt and was ejected towards the interior of the Solar System, where later encounters with Jupiter successively changed its orbit.

Up to 1840, the comet's perihelion distance was 4 AU (600 million km), too far for the Sun to vaporize the nucleus. In 1840 Jupiter changed the orbit to a perihelion distance of 3 AU (450 million km), and later encounters further decreased that distance to 2.77 AU (414 million km).[43]

In February 1959, a close encounter with Jupiter[44] moved Churyumov–Gerasimenko's perihelion inward to about 1.29 AU (193 million km), where it remains today.[14][43]

Before Churyumov–Gerasimenko's perihelion passage in 2009, its rotational period was 12.76 hours. During this perihelion passage, it decreased to 12.4 hours, which likely happened because of sublimation-induced torque.[7]

2015 perihelion

As of September 2014, Churyumov–Gerasimenko's nucleus had an apparent magnitude of roughly 20.[13] It came to perihelion on 13 August 2015.[2][12] From December 2014 until September 2015, it had an elongation less than 45 degrees from the Sun.[45] On 10 February 2015, it went through solar conjunction when it was 5 degrees from the Sun and was 3.3 AU (490 million km) from Earth.[45] It crossed the celestial equator on 5 May 2015 and became easiest to see from the Northern Hemisphere.[45] Even right after perihelion when it was in the constellation of Gemini, it only brightened to about apparent magnitude 12, and required a telescope to be seen.[12] As of July 2016, the comet had a total magnitude of about 20.[13]

Rosetta mission

Churyumov–Gerasimenko was the destination of the Rosetta mission, launched in 2004, which rendezvoused with it in 2014 and was the first mission to land a space probe on a comet.

Advance work

Rosetta's first sighting of its target in 2014 – narrow angle view (14813677376)
First image of the comet taken by Rosetta with Messier 107 in view, 21 March 2014

As preparation for the Rosetta mission, Hubble Space Telescope pictures taken on 12 March 2003 were closely analysed. An overall 3D model was constructed and computer-generated images were created.[46]

On 25 April 2012, the most detailed observations until that time were taken with the 2-metre Faulkes Telescope by N. Howes, G. Sostero and E. Guido while it was at its aphelion.

On 6 June 2014, water vapor was detected being released at a rate of roughly 1 L/s (0.26 USgal/s) when Rosetta was 360,000 km (220,000 mi) from Churyumov–Gerasimenko and 3.9 AU (580 million km) from the Sun.[47][48] On 14 July 2014, images taken by Rosetta showed that its nucleus is irregular in shape with two distinct lobes. Two explanations were proposed at the time: that its shape may have resulted from asymmetric erosion due to ice sublimating from its surface to leave behind its lobed shape. Newer evidence supports the contact binary model. The size of the nucleus was estimated to be 3.5×4 km (2.2×2.5 mi).[17][49][50]

Rendezvous and orbit

Animation of Rosetta trajectory
Animation of Rosetta's trajectory from 2 March 2004 to 9 September 2016
  Rosetta ·   67P ·   Earth ·   Mars ·   21 Lutetia ·   2867 Šteins
Animation of Rosetta trajectory around 67P
Animation of Rosetta's orbit around 67P from 1 August 2014 to 31 March 2015
  Rosetta ·   67P

Beginning in May 2014, Rosetta's velocity was reduced by 780 m/s (2,800 km/h; 1,700 mph) with a series of thruster firings.[17][51] Ground controllers rendezvoused Rosetta with Churyumov–Gerasimenko on 6 August 2014.[18][19] This was done by reducing Rosetta's relative velocity to 1 m/s (4 km/h; 2 mph). Rosetta entered orbit on 10 September, at about 30 km (19 mi) from the nucleus.[18][19][52]

Landing

Descent of a small lander occurred on 12 November 2014. Philae is a 100 kg (220 lb) robotic probe that set down on the surface with landing gear.[17][53] The landing site has been christened Agilkia in honour of Agilkia Island, where the temples of Philae Island were relocated after the construction of the Aswan Dam flooded the island.[54] The acceleration due to gravity on the surface of Churyumov–Gerasimenko has been estimated for simulation purposes at 10−3 m/s2,[55] or about one ten-thousandth of that on Earth.

Because of its low relative mass, landing on the comet involved certain technical considerations to keep Philae anchored. The probe contains an array of mechanisms designed to manage Churyumov–Gerasimenko's low gravity, including a cold gas thruster, harpoons, landing-leg-mounted ice screws, and a flywheel to keep it oriented during its descent.[56][57][58] During the event, the thruster and the harpoons failed to operate, and the ice screws did not gain a grip. The lander bounced twice and only came to rest when it made contact with the surface for the third time,[59] two hours after first contact.[60]

Contact with Philae was lost on 15 November 2014 because of dropping battery power. The European Space Operations Centre briefly reestablished communications on 14 June 2015 and reported a healthy spacecraft but communications were lost again soon after.[61] On 2 September 2016, Philae was located in photographs taken by the Rosetta orbiter. It had come to rest in a crack with only its body and two legs visible. While the discovery solves the question of the lander's disposition, it also allows project scientists to properly contextualise the data it returned from the comet's surface.[62]

Science

Crescent Comet 67P
False colour image of the comet outgassing, 15 April 2015

The composition of water vapor from Churyumov–Gerasimenko, as determined by the Rosetta spacecraft, is substantially different from that found on Earth. The ratio of deuterium to hydrogen in the water from the comet was determined to be three times that found for terrestrial water. This makes it unlikely that water found on Earth came from comets such as Churyumov–Gerasimenko.[9][63][64] On 22 January 2015, NASA reported that, between June and August 2014, the comet released increasing amounts of water vapor, up to tenfold as much.[65] On 23 January 2015, the journal Science published a special issue of scientific studies related to the comet.[66]

Measurements carried out before Philae's batteries failed indicate that the dust layer could be as much as 20 cm (8 in) thick. Beneath that is hard ice, or a mixture of ice and dust. Porosity appears to increase toward the center of the comet.[67]

The nucleus of Churyumov–Gerasimenko was found to have no magnetic field of its own after measurements were taken during Philae's descent and landing by its ROMAP instrument and Rosetta's RPC-MAG instrument. This suggests that magnetism may not have played a role in the early formation of the Solar System, as had previously been hypothesized.[68][69]

The ALICE spectrograph on Rosetta determined that electrons (within 1 km or 0.6 mi above the comet nucleus) produced from photoionization of water molecules by solar radiation, and not photons from the Sun as thought earlier, are responsible for the degradation of water and carbon dioxide molecules released from the comet nucleus into its coma.[70][71] Also, active pits, related to sinkhole collapses and possibly associated with outbursts are present on the comet.[72][73]

Measurements by the COSAC and Ptolemy instruments on the Philae's lander revealed sixteen organic compounds, four of which were seen for the first time on a comet, including acetamide, acetone, methyl isocyanate and propionaldehyde.[74][75][76] Astrobiologists Chandra Wickramasinghe and Max Wallis stated that some of the physical features detected on the comet's surface by Rosetta and Philae, such as its organic-rich crust, could be explained by the presence of extraterrestrial microorganisms.[77][78] Rosetta program scientists dismissed the claim as "pure speculation".[79] Carbon-rich compounds are common in the Solar System. Neither Rosetta nor Philae is equipped to search for direct evidence of organisms.[77] The only amino acid detected thus far on the comet is glycine, along with precursor molecules methylamine and ethylamine.[80]

Solid organic compounds were also found in the dust particles emitted by the comet; the carbon in this organic material is bound in "very large macromolecular compounds", analogous to the insoluble organic matter in carbonaceous chondrite meteorites. Scientists think that the observed cometary carbonaceous solid matter could have the same origin as the meteoritic insoluble organic matter, but suffered less modification before or after being incorporated into the comet.[81]

One of the most outstanding discoveries of the mission so far is the detection of large amounts of free molecular oxygen (O
2
) gas surrounding the comet. Current solar system models suggest the molecular oxygen should have disappeared by the time 67P was created, about 4.6 billion years ago in a violent and hot process that would have caused the oxygen to react with hydrogen and form water.[82][83] Molecular oxygen has never before been detected in cometary comas. In situ measurements indicate that the O
2
/H
2
O ratio is isotropic in the coma and does not change systematically with heliocentric distance, suggesting that primordial O
2
was incorporated into the nucleus during the comet's formation.[82] Detection of molecular nitrogen (N
2
) in the comet suggests that its cometary grains formed in low-temperature conditions below 30 K (−243 °C; −406 °F).[84]

On 3 July 2018, researchers reported that molecular oxygen is not made on the surface of comet 67P, a finding that supports the notion that the oxygen comes from the body of the comet, and may be primordial.[85][86]

Future missions

CAESAR is a proposed sample-return mission aimed at returning to 67P/Churyumov–Gerasimenko, capturing regolith from the surface, and returning it to Earth.[87][88] This mission is competing in NASA's New Frontiers mission 4 selection process, and as of December 2017 is one of two finalists in the program.[89]

Gallery

67PNucleus

A reconstruction of the nucleus's shape based on Hubble observations in 2003

VLT Tracks Rosetta's Comet

As seen by the Very Large Telescope on 11 August 2014[90]

Comet 67P on 22 August 2014 NavCam

As seen by Rosetta on 22 August 2014

Comet 67P on 14 September 2014 NavCam mosaic

As seen by Rosetta on 14 September 2014

67P-C-G - March 25 2015 (32628887201)

As seen by Rosetta on 25 March 2015

67P-C-G - March 28 2015 (32370930490)

As seen by Rosetta on 28 March 2015

67P-C-G - May 2 2015 (32730086746)

As seen by Rosetta on 2 May 2015

Comet on 7 July 2015 NavCam

As seen by Rosetta on 7 July 2015

Cliffs of Comet 67P

Image showing ragged cliffs, 10 December 2014

See also

References

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Further reading

External links

Numbered comets
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67P/Churyumov–Gerasimenko Next
68P/Klemola
140 Siwa

Siwa (; minor planet designation: 140 Siwa) is a large and dark main-belt asteroid that was discovered by Austrian astronomer Johann Palisa on October 13, 1874, and named after Šiwa, the Slavic goddess of fertility.

The Rosetta comet probe was to visit Siwa on its way to comet 46P/Wirtanen in July, 2008. However, the mission was rerouted to comet 67P/Churyumov-Gerasimenko and the flyby had to be abandoned.Attempts to measure the rotation period of this asteroid have produced inconsistent results ranging from 14.7 to 32 hours. Photometric observations of this asteroid at the Organ Mesa Observatory in Las Cruces, New Mexico during 2010 gave an irregular light curve with a period of 34.407 ± 0.002 hours and a brightness variation of 0.05 ± 0.01 in magnitude.A 2004 study of the spectrum matched a typical C-type asteroid with typical carbonaceous chondrite makeup. There are no absorption features of mafic minerals found. The classification was later revised to a P-type asteroid.

46P/Wirtanen

46P/Wirtanen is a small short-period comet with a current orbital period of 5.4 years. It was the original target for close investigation by the Rosetta spacecraft, planned by the European Space Agency, but an inability to meet the launch window caused Rosetta to be sent to 67P/Churyumov–Gerasimenko instead. It belongs to the Jupiter family of comets, all of which have aphelia between 5 and 6 AU. Its diameter is estimated at 1.2 kilometres (0.75 mi).

757 Portlandia

757 Portlandia is a main-belt asteroid 32 km in diameter. In November 2015 amateur astronomers where photographing it in images of comet 67P/Churyumov–Gerasimenko. Portlandia will come to opposition in March 2016 at apparent magnitude 13.2.

CAESAR (spacecraft)

CAESAR (Comet Astrobiology Exploration Sample Return) is a proposed sample-return mission to comet 67P/Churyumov–Gerasimenko. The mission was proposed in 2017 to NASA's New Frontiers program mission 4, and on 20 December 2017 it was one of two finalists selected for further concept development.

If selected in July 2019, it may launch between 2024 and 2025, with a capsule delivering a sample back to Earth in 2038. The Principal Investigator is Steve Squyres of Cornell University in Ithaca, New York. CAESAR would be managed by NASA's Goddard Space Flight Center in Greenbelt, Maryland. Curation of the returned sample would take place at NASA's Astromaterials Research and Exploration Science Directorate, based at Johnson Space Center in Houston, Texas.

The CAESAR team chose comet 67P over other cometary targets in part because the data collected by the Rosetta mission, which studied the comet from 2014 to 2016, allows the spacecraft to be designed to the conditions there, increasing the mission's chance of success. The Rosetta mission also provides a vast geologic context for this mission's sample-return analysis.

Coma (cometary)

The coma is the nebulous envelope around the nucleus of a comet, formed when the comet passes close to the Sun on its highly elliptical orbit; as the comet warms, parts of it sublime. This gives a comet a "fuzzy" appearance when viewed in telescopes and distinguishes it from stars. The word coma comes from the Greek "kome" (κόμη), which means "hair" and is the origin of the word comet itself.The coma is generally made of ice and comet dust. Water dominates up to 90% of the volatiles that outflow from the nucleus when the comet is within 3-4 AU of the Sun. The H2O parent molecule is destroyed primarily through photodissociation and to a much smaller extent photoionization. The solar wind plays a minor role in the destruction of water compared to photochemistry. Larger dust particles are left along the comet's orbital path while smaller particles are pushed away from the Sun into the comet's tail by light pressure.

On 11 August 2014, astronomers released studies, using the Atacama Large Millimeter/Submillimeter Array (ALMA) for the first time, that detailed the distribution of HCN, HNC, H2CO, and dust inside the comae of comets C/2012 F6 (Lemmon) and C/2012 S1 (ISON). On 2 June 2015, NASA reported that the ALICE spectrograph on the Rosetta space probe studying comet 67P/Churyumov–Gerasimenko determined that electrons (within 1 km (0.62 mi) above the comet nucleus) produced from photoionization of water molecules by solar radiation, and not photons from the Sun as thought earlier, are responsible for the degradation of water and carbon dioxide molecules released from the comet nucleus into its coma.

Comet Nucleus Dust and Organics Return

COmet Nucleus Dust and Organics Return (CONDOR) is a mission concept to retrieve a sample from comet 67P/Churyumov–Gerasimenko to test ideas regarding Solar System formation, and accretion of rocky planets with habitable surface environments.

CONDOR is a concept by a NASA's Jet Propulsion Laboratory team led by Christopher Guethe and M. Choukroun.

Comet nucleus

The nucleus is the solid, central part of a comet, popularly termed a dirty snowball or an icy dirtball. A cometary nucleus is composed of rock, dust, and frozen gases. When heated by the Sun, the gases sublimate and produce an atmosphere surrounding the nucleus known as the coma. The force exerted on the coma by the Sun's radiation pressure and solar wind cause an enormous tail to form, which points away from the Sun. A typical comet nucleus has an albedo of 0.04. This is blacker than coal, and may be caused by a covering of dust.Results from the Rosetta and Philae spacecraft show that the nucleus of 67P/Churyumov–Gerasimenko has no magnetic field, which suggests that magnetism may not have played a role in the early formation of planetesimals. Further, the ALICE spectrograph on Rosetta determined that electrons (within 1 km (0.62 mi) above the comet nucleus) produced from photoionization of water molecules by solar radiation, and not photons from the Sun as thought earlier, are responsible for the degradation of water and carbon dioxide molecules released from the comet nucleus into its coma. On 30 July 2015, scientists reported that the Philae spacecraft, that landed on comet 67P/Churyumov-Gerasimenko in November 2014, detected at least 16 organic compounds, of which four (including acetamide, acetone, methyl isocyanate and propionaldehyde) were detected for the first time on a comet.

Continuum (Ligeti)

Continuum for harpsichord is a musical composition by György Ligeti composed in 1968, and dedicated to the contemporary harpsichordist, Antoinette Vischer. The composer describes the conception and result of its technique:

I thought to myself, what about composing a piece that would be a paradoxically continuous sound, something like Atmosphères, but that would have to consist of innumerable thin slices of salami? A harpsichord has an easy touch; it can be played very fast, almost fast enough to reach the level of continuum, but not quite (it takes about eighteen separate sounds per second to reach the threshold where you can no longer make out individual notes and the limit set by the mechanism of the harpsichord is about fifteen to sixteen notes a second). As the string is plucked by the plectrum, apart from the tone you also hear quite a loud noise. The entire process is a series of sound impulses in rapid succession which create the impression of continuous sound.

Amy Bauer (2004, p. 130) describes the piece as trompe-l'œil, creating "a sense of stasis through extremely rapid activity." She compares it to a patient's description of the schizophrenic experience of, "an intense cerebral activity in which inner experiences took place at greatly increased speed, so that much more than usual happened per minute of external time. The result was to give an effect of slow motion." (Sass 1992)

This piece has also been arranged for barrel organ and for two player pianos by the composer.

The piece has also been compared by classical music reviewers to the magnetic fluctuations of comet 67P/Churyumov–Gerasimenko as detected by the space probe Philae after the fluctuations were artistically sonificated by a German composer and sound designer to make them audible.

Enceladus Life Signatures and Habitability

Enceladus Life Signatures and Habitability (ELSAH) is an astrobiology concept mission proposed in 2017 to NASA's New Frontiers program to send a spacecraft to Enceladus to search for biosignatures and assess its habitability. The Principal Investigator is Christopher P. McKay, an astrobiologist at NASA Ames Research Center, and the managing NASA center is Goddard Space Flight Center. No details of the mission have been made public, but observers speculate that it would be a plume-sampling orbiter mission.The two finalists, announced on 20 December 2017, are Dragonfly to Titan, and CAESAR (Comet Astrobiology Exploration Sample Return) which is a sample-return mission from comet 67P/Churyumov–Gerasimenko.Although ELSAH was not selected for launch in this instance, it received technology development funds to prepare it for future mission competitions. The funds are meant to develop techniques that limit spacecraft contamination and thereby enable life detection measurements on cost-capped missions.

Hibernation (spacecraft)

Hibernation, as employed with reference to spacecraft, is a mode used when regular operations are suspended for an extended period of time but when restarting is expected (unlike termination). It is typically used for long duration and deep space missions in order to save power or other limited resources and extend mission life. The term is substantially similar to the hibernation mode used in computer power saving.

Rosetta, a mission to study comet 67P/Churyumov–Gerasimenko (67P), was placed into hibernation for 31 months to conserve its limited resources when is ventured near the orbit of Jupiter while en route to its rendezvous. The New Horizons mission, which entered hibernation mode many times on its way to Pluto and then again while en route to 2014_MU69, features a hibernation mode included some amount of health and status monitoring and occasional wake-ups to check and calibrate instruments. NASA's Wide-field Infrared Survey Explorer mission, originally operated by the agency's astrophysics division for an infrared all-sky survey, was placed into hibernation in 2011 and then reawakened in 2013 in order to conduct an asteroid survey by the planetary science division.

Hot Bird 7

Hot Bird 7 was a French communications satellite which was lost in a launch failure in 2002. Intended for operation by Eutelsat, it was to have provided direct to home broadcasting services from geostationary orbit as part of Eutelsat's Hot Bird constellation at a longitude of 13 degrees east. Hot Bird 7 was intended to replace the Hot Bird 3 satellite which had been launched in 1997.Hot Bird 7 was constructed by Astrium, and was based on the Eurostar-2000+ satellite bus. It had a mass of 3,400 kilograms (7,500 lb) and was expected to have an operational lifespan of 15 years. The spacecraft was equipped with 40 Ku-band transponders, for broadcasting satellite television and radio. It would have broadcast to homes in Europe, the Middle East and North Africa.

Arianespace was contracted to launch Hot Bird 7 on the maiden flight of the Ariane 5 ECA carrier rocket, an upgraded version of the Ariane 5 intended to offer increased payload capacity to geosynchronous transfer orbit. The Stentor technology demonstration satellite, to have been operated by the French space agency CNES, was also aboard the rocket. The launch took place from ELA-3 at Kourou, French Guiana, at 22:22 UTC on 11 December 2002, bound for geosynchronous transfer orbit.

Around three minutes after liftoff, performance issues with the first stage's Vulcain 2 engine — which was making its first flight — began to be noted. By the time of fairing separation, 183 seconds into the flight, the rocket was tumbling out of control. It began to lose altitude and speed, before being destroyed by range safety 456 seconds after launch. The failure was attributed to an engine cooling problem which developed around 96 seconds into the mission, causing the engine to destroy itself. Due to the failure the next Ariane 5 launch, which had been scheduled to carry the European Space Agency's Rosetta spacecraft in January 2003, was delayed - causing Rosetta to miss its launch window for a mission to comet 46P/Wirtanen. Rosetta was subsequently retargeted to 67P/Churyumov–Gerasimenko and launched successfully in 2004.

Interstellar ice

Interstellar ice consists of grains of volatiles in the ice phase that form in the interstellar medium. Ice and dust grains form the primary material out of which the Solar System was formed. Grains of ice are found in the dense regions of molecular clouds, where new stars are formed. Temperatures in these regions can be as low as 10 K (−263 °C; −442 °F), allowing molecules that collide with grains to form an icy mantle. Thereafter, atoms undergo thermal motion across the surface, eventually forming bonds with other atoms. This results in the formation of water and methanol. Indeed, the ices are dominated by water and methanol, as well as ammonia, carbon monoxide and carbon dioxide. Frozen formaldehyde and molecular hydrogen may also be present. Found in lower abundances are nitriles, ketones, esters and carbonyl sulfide. The mantles of interstellar ice grains are generally amorphous, only becoming crystalline in the presence of a star.The composition of interstellar ice can be determined through its infrared spectrum. As starlight passes through a molecular cloud containing ice, molecules in the cloud absorb energy. This adsorption occurs at the characteristic frequencies of vibration of the gas and dust. Ice features in the cloud are relatively prominently in this spectra, and the composition of the ice can be determined by comparison with samples of ice materials on Earth. In the sites directly observable from Earth, around 60–70% of the interstellar ice consists of water, which displays a strong emission at 3.05 μm from stretching of the O–H bond.In September 2012, NASA scientists reported that polycyclic aromatic hydrocarbons (PAHs), subjected to interstellar medium (ISM) conditions, are transformed, through hydrogenation, oxygenation and hydroxylation, to more complex organics - "a step along the path toward amino acids and nucleotides, the raw materials of proteins and DNA, respectively". Further, as a result of these transformations, the PAHs lose their spectroscopic signature which could be one of the reasons "for the lack of PAH detection in interstellar ice grains, particularly the outer regions of cold, dense clouds or the upper molecular layers of protoplanetary disks."

Ivano Bertini

Ivano Bertini (born April, 1968, in Milan, Italy) is an Italian astronomer at the University of Padua.

Klim Churyumov

Klim Ivanovich Churyumov (Ukrainian: Клим Іва́нович Чурю́мов, Russian: Клим Ива́нович Чурю́мов) (19 February 1937 – 14 October 2016) was a Soviet and Ukrainian astronomer.Director of the Kiev Planetarium, member of the National Academy of Sciences of Ukraine, the International Astronomical Union, of the New York Academy of Sciences, editor of the magazine "Our Skies" (Ukrainian: Наше Небо) in 2006-2009, president of the Ukrainian Society of amateur astronomy and author of books for children.

In 1969 he discovered, with Svetlana Gerasimenko, the comet 67P/Churyumov–Gerasimenko; on 12 November 2014 the Rosetta space mission landed its Philae spacecraft on its surface.

List of extraterrestrial dune fields

This is a list of dune fields not on Earth which have been given official names by the International Astronomical Union. Dune fields are named according to the IAU's rules of planetary nomenclature. The relevant descriptor term is undae. As of now, the only two solar system planets, besides Earth, with named dune fields are Venus and Mars. Dune fields have also been discovered on Saturn's moon Titan, and a field of giant ripples has been identified on comet 67P/Churyumov–Gerasimenko.

Micro-Imaging Dust Analysis System

The Micro-Imaging Dust Analysis System (MIDAS) is one of several instruments on the European Space Agency's Rosetta mission which studied in-situ the environment around the active comet 67P/Churyumov–Gerasimenko as it flew into the inner Solar System. MIDAS is an atomic force microscope (AFM) designed to collect dust particles emitted from the comet, and then scan them with a very sharp needle-like tip to determine their 3D structure, size and texture with very high resolution (4 nanometers).

Rosetta (spacecraft)

Rosetta was a space probe built by the European Space Agency launched on 2 March 2004. Along with Philae, its lander module, Rosetta performed a detailed study of comet 67P/Churyumov–Gerasimenko (67P). During its journey to the comet, the spacecraft flew by Mars and the asteroids 21 Lutetia and 2867 Šteins. It was launched as the third cornerstone mission of the ESA's Horizon 2000 programme, after SOHO / Cluster and XMM-Newton.

On 6 August 2014, the spacecraft reached the comet and performed a series of manoeuvres to eventually orbit the comet at distances of 30 to 10 kilometres (19 to 6 mi). On 12 November, its lander module Philae performed the first successful landing on a comet, though its battery power ran out two days later. Communications with Philae were briefly restored in June and July 2015, but due to diminishing solar power, Rosetta's communications module with the lander was turned off on 27 July 2016. On 30 September 2016, the Rosetta spacecraft ended its mission by hard-landing on the comet in its Ma'at region.The probe was named after the Rosetta Stone, a stele of Egyptian origin featuring a decree in three scripts. The lander was named after the Philae obelisk, which bears a bilingual Greek and Egyptian hieroglyphic inscription.

SED Systems

SED Systems is a communications company supplying both systems and services to the satellite industry. Originating in 1965, SED is located in the Innovation Place Research Park on the University of Saskatchewan campus. As an operating division of the Calian Group Ltd. (TSX:CGY), SED employs approximately 280 employees and annually achieves sales of over 80 million dollars.

SED serves an international market that includes government defense departments, space organizations as well as commercial customers such as Boeing Satellite Systems, Hughes Network Systems, Inmarsat and Sirius XM Satellite Radio.Between 2001 and 2013, SED Systems provided the European Space Agency (ESA) with 3 deep-space antennas, the New Norcia Station, Australia (DSA 1), the Cebreros Station, Spain (DSA 2), and Malargüe Station, Argentina (DSA 3). These are some of the largest antennas in the world, spanning 35 meters, allowing the ESA to track missions such as Rosetta (spacecraft) and the Philae (spacecraft) landing on comet 67P/Churyumov–Gerasimenko in 2014.Canada played an active role in the research and development of the International Space Station (ISS) with endeavors such as the Mobile Servicing System (MSS). SED Systems was a part of the Mobile Servicing System program developed the Shuttle Remote Manipulator System (SRMS), or Canadarm 2. The Canadarm 1 was developed by a team led by Spar Aerospace Special Products and Advance Research Division of De Havilland Canada, in which SED Systems also played a key role.

Svetlana Gerasimenko

Svetlana Ivanovna Gerasimenko (Russian: Светла́на Ива́новна Герасиме́нко; Ukrainian: Світлана Іванівна Герасименко) is a Soviet and Tajikistani astronomer of Ukrainian origin and discoverer of comet 67P/Churyumov–Gerasimenko.

Rosetta mission
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2014 in space
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