APOD Wall Calendar 2015 Moons and Planets

APOD Wall Calendar
2015
Moons and Planets
This image credit:
NASA, JPL-Caltech, MSSS; Digital processing: Damia Bouic
Two Hours Before Neptune
Credit: Voyager 2, NASA
Explanation: Two hours before closest approach to Neptune in 1989, the Voyager 2 robot spacecraft snapped this picture. Clearly visible for the first time were long light-colored cirrus-type clouds
floating high in Neptune's atmosphere. Shadows of these clouds can even be seen on lower cloud decks. Most of Neptune's atmosphere is made of hydrogen and helium, which is invisible.
Neptune's blue color therefore comes from smaller amounts of atmospheric methane, which preferentially absorbs red light. Neptune has the fastest winds in the Solar System, with gusts
reaching 2000 kilometers per hour. Speculation holds that diamonds may be created in the dense hot conditions that exist under the cloud tops of Uranus and Neptune.. APOD: 2010 August 8 .
2014
January
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December
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August
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November
October
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July
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June
September
F
Crossing Dingo Gap on Mars
Explanation: An important threshold on Mars has now been crossed. Landing in mid-2012, the Curiosity rover is searching for clues of whether life could ever have existed on the red planet.
Recent findings of Curiosity include evidence for an ancient (but now dried) freshwater lake, and the non-detection of the biomarker methane in the Martian atmosphere. To continue its
investigation, the car-sized rover is on an expedition to roll up Mt. Sharp, the central peak of the large crater in which it landed. Life might have shown preference for water that once ran down
the Martian mountain. Two weeks ago, to avoid more dangerous and rocky terrain, Curiosity was directed to roll across a one-meter high sand dune that blocked a useful entrance to Mt. Sharp.
Just after the short trip over Dingo Gap was successful, the robotic rover took the above image showing the now-traversed sand mound covered with its wheel tracks. APOD: 2014 February 18
January 2015
Sunday
Monday
Tuesday
Wednesday
Thursday
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Friday
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Saturday
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Quadrantids meteor shower
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Earth closest to Sun
Quadrantids meteor shower
Credit: ESA / Rosetta / MPS for OSIRIS Team; MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
Rosetta's Rendezvous
Explanation: On 2014 August 3rd, the Rosetta spacecraft's
narrow angle camera captured this stunning image of the
nucleus of Comet 67P/Churyumov-Gerasimenko. After 10
years and 6.5 billion kilometers of travel along gravity assist
trajectories looping through interplanetary space, Rosetta had
approached to within 285 kilometers of its target. The curious
double-lobed shape of the nucleus is revealed in amazing detail
at an image resolution of 5.3 meters per pixel. About 4
kilometers across, the comet nucleus is presently just over 400
million kilometers from Earth, between the orbits of Jupiter
and Mars. Now the first spacecraft to achieve a delicate orbit
around a comet, Rosetta will swing to within 50 kilometers and
closer in the coming weeks, identifiying candidate sites for
landing its probe Philae later in 2014. APOD: 2014 August 7
February 2015
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Dawn approaches Ceres
Saturday
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Jupiter brightest
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Venus nearest Mars
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Io in True Color
Credit: Galileo Project, JPL, NASA
Explanation: The strangest moon in the Solar System is bright yellow. This picture, an attempt to show how Io would appear in the "true colors" perceptible to the average human eye, was taken in
1999 July by the Galileo spacecraft that orbited Jupiter from 1995 to 2003. Io's colors derive from sulfur and molten silicate rock. The unusual surface of Io is kept very young by its system of active
volcanoes. The intense tidal gravity of Jupiter stretches Io and damps wobbles caused by Jupiter's other Galilean moons. The resulting friction greatly heats Io's interior, causing molten rock to
explode through the surface. Io's volcanoes are so active that they are effectively turning the whole moon inside out. Some of Io's volcanic lava is so hot it glows in the dark. APOD: 2014 March 30
March 2015
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Total Solar Eclipse
Equinox
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Saturn in Blue and Gold
Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA
Explanation: Why is Saturn partly blue? The above picture of Saturn approximates what a human would see if hovering close to the giant ringed world. The above picture was taken in 2006
March by the robot Cassini spacecraft now orbiting Saturn. Here Saturn's majestic rings appear directly only as a thin vertical line. The rings show their complex structure in the dark shadows
they create on the image left. Saturn's fountain moon Enceladus, only about 500 kilometers across, is seen as the bump in the plane of the rings. The northern hemisphere of Saturn can appear
partly blue for the same reason that Earth's skies can appear blue -- molecules in the cloudless portions of both planet's atmospheres are better at scattering blue light than red. When looking
deep into Saturn's clouds, however, the natural gold hue of Saturn's clouds becomes dominant. It is not known why southern Saturn does not show the same blue hue -- one hypothesis holds
that clouds are higher there. It is also not known why Saturn's clouds are colored gold. APOD: 2014 April 13
April 2015
Sunday
Monday
Tuesday
Wednesday
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Thursday
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Saturday
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Total Lunar Eclipse
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Lyrids Meteor Shower
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Lyrids Meteor Shower
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Jupiter's Great Red Spot from Voyager 1
Explanation: What will become of Jupiter's Great Red Spot? Recorded as shrinking since the 1930s, the rate of the Great Red Spot's size appears to have accelerated just in the past few years. A
hurricane larger than Earth, the Great Red Spot has been raging at least as long as telescopes could see it. Like most astronomical phenomena, the Great Red Spot was neither predicted nor
immediately understood after its discovery. Although small eddies that feed into the storm system seem to play a role, a more full understanding of the gigantic storm cloud remains a topic of
continued research, and may result in a better understanding of weather here on Earth. The above image is a digital enhancement of an image of Jupiter taken in 1979 by the Voyager 1 spacecraft
as it zoomed by the Solar System's largest planet. NASA's Juno spacecraft is currently heading toward Jupiter and will arrive in 2016. APOD: 2014 May 18
May 2015
Sunday
3
Monday
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Tuesday
Wednesday
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6
Eta Aquariids Meteor Shower
Eta Aquariids Meteor Shower
Thursday
Friday
Saturday
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Saturn brightest
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31
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Image Credit: NASA, JPL-Caltech, MSSS
Martian Anniversary Selfie
Explanation: June 24th 2014 marked the
first full Martian year of the Curiosity
Rover's exploration of the surface of
the Red Planet. That's 687 Earth days or
669 sols since its landing on August 5,
2012. To celebrate, consider this selfportrait of the car-sized robot posing
next to a rocky outcrop dubbed
Windjana, its recent drilling and
sampling site. The mosaicked selfie was
constructed with frames taken this April
and May using the rover's Mars Hand
Lens Imager (MAHLI), intended for
close-up work and mounted at the end
of the rover's robotic arm. The MAHLI
frames used exclude sections that show
the arm itself and so MAHLI and the
robotic arm are not seen. Famous for
panoramic views, the rover's Mastcam
is visible though, on top of the tall mast
staring toward the left and down at the
drill hole. APOD: 2014 June 27
June 2015
Sunday
Monday
Tuesday
Wednesday
Thursday
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Saturday
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Solstice
28
Venus nearest Jupiter
The Moon from Zond 8
© Galspace
Explanation: Which moon is this? Earth's. Our Moon's unfamiliar appearance is due partly to an unfamiliar viewing angle as captured by a little-known spacecraft -- the Soviet Union's Zond 8
that circled the Moon in October of 1970. Pictured above, the dark-centered circular feature that stands out near the top of the image is Mare Orientale, a massive impact basin formed by an
ancient collision with an asteroid. Mare Orientale is surrounded by light colored and highly textured highlands. Across the image bottom lies the dark and expansive Oceanus Procellarum, the
largest of the dark (but dry) maria that dominate the side of the Moon that always faces toward the Earth. Originally designed to carry humans, robotic Zond 8 came within 1000 km of the lunar
surface, took about 100 detailed photographs on film, and returned them safely to Earth within a week. APOD: 2013 July 16
July 2015
Sunday
Monday
Tuesday
Wednesday
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Thursday
Friday
Saturday
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Venus nearest Jupiter
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Earth furthest from Sun
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New Horizons passes Pluto
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Delta Aquariids Meteor Shower
Delta Aquariids Meteor Shower
Venus near Jupiter
Fresh Tiger Stripes on Saturn's Enceladus
Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA
Explanation: Do underground oceans vent through the tiger stripes on Saturn's moon Enceladus? Long features dubbed tiger stripes are known to be spewing ice from the moon's icy interior into
space, creating a cloud of fine ice particles over the moon's South Pole and creating Saturn's mysterious E-ring. Evidence for this has come from the robot Cassini spacecraft now orbiting Saturn.
Pictured above, a high resolution image of Enceladus is shown from a close flyby. The unusual surface features dubbed tiger stripes are visible in false-color blue. Why Enceladus is active remains a
mystery, as the neighboring moon Mimas, approximately the same size, appears quite dead. Most recently, an analysis of slight gravity deviations has given an independent indication of
underground oceans. Such research is particularly interesting since such oceans would be candidates to contain life. APOD: 2014 April 6
August 2015
Sunday
Monday
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Saturday
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Perseids Meteor Shower
Perseids Meteor Shower
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Venus nearest Mars
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Venus nearest Mars
Saturn, Titan, Rings, and Haze
Image Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA
Explanation: This is not a solar eclipse. Pictured above is a busy vista of moons and rings taken at Saturn. The large circular object in the center of the image is Titan, the largest moon of Saturn and
one of the most intriguing objects in the entire Solar System. The dark spot in the center is the main solid part of the moon. The bright surrounding ring is atmospheric haze above Titan, gas that is
scattering sunlight to a camera operating onboard the robotic Cassini spacecraft. Cutting horizontally across the image are the rings of Saturn, seen nearly edge on. At the lower right of Titan is
Enceladus, a small moon of Saturn. Since the image was taken pointing nearly at the Sun, the surfaces of Titan and Enceladus appear in silhouette, and the rings of Saturn appear similar to a
photographic negative. Now if you look really really closely at Enceladus, you can see a hint of icy jets shooting out toward the bottom of the image. It is these jets that inspired future proposals to
land on Enceladus, burrow into the ice, and search for signs of extraterrestrial life.. APOD: 2013 July 29
September 2015
Sunday
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Saturday
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Partial Solar Eclipse
20
Equinox
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Total Lunar Eclipse
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Mercury in Accentuated Color
Credit: MESSENGER, NASA, JHU APL, CIW
Explanation: The colors of Mercury are subtle but beautiful. At first glance, our Solar System's innermost planet appears simply black and white, but images that include infrared colors
normally beyond human vision accentuate a world of detail. One such image, shown above, was acquired by the robotic MESSENGER spacecraft that swung by Mercury in mid-January. Here,
most generally, the hot world itself acquires a slightly more brown hue. Many craters that appear on top of other craters -- and so surely have formed more recently -- appear here as bright
with bright rays that include a slightly blue tint, indicating that soil upended during the impact was light in color. A few craters, such as some in the huge Caloris Basin impact feature visible on
the upper right, appear unexpectedly to be ringed with a dark material, the nature of which is being researched. MESSENGER continues to glide through the inner Solar System and will pass
Mercury again this October and next September, before entering orbit around the desolate world in 2011. APOD: 2008 March 19
October 2015
Sunday
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Saturday
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Mars nearest Jupiter
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Orionids Meteor Shower
25
Venus nearest Jupiter
26
Venus nearest Jupiter
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Venus near Mars & Jupiter
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Orionids Meteor Shower
29
Venus' Once Molten Surface
Credit: E. De Jong et al. (JPL), MIPL, Magellan Team, NASA
Explanation: If you could look across Venus with radar eyes, what might you see? This computer reconstruction of the surface of Venus was created from data from the Magellan spacecraft.
Magellan orbited Venus and used radar to map our neighboring planet's surface between 1990 and 1994. Magellan found many interesting surface features, including the large circular domes,
typically 25-kilometers across, that are depicted above. Volcanism is thought to have created the domes, although the precise mechanism remains unknown. Venus' surface is so hot and hostile
that no surface probe has lasted more than a few minutes. APOD: 2013 June 23
November 2015
Sunday
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Venus nearest Mars
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Leonids Meteor Shower
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Leonids Meteor Shower
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Gibbous Europa
Credit: Galileo Project, JPL, NASA; Copyright: reprocessed by Ted Stryk
Explanation: Although the phase of this moon might appear familiar, the moon itself might not. In fact, this gibbous phase shows part of Jupiter's moon Europa. The robot spacecraft Galileo captured
this image mosaic during its mission orbiting Jupiter from 1995 - 2003. Visible are plains of bright ice, cracks that run to the horizon, and dark patches that likely contain both ice and dirt. Raised
terrain is particularly apparent near the terminator, where it casts shadows. Europa is nearly the same size as Earth's Moon, but much smoother, showing few highlands or large impact craters.
Evidence and images from the Galileo spacecraft, indicated that liquid oceans might exist below the icy surface. To test speculation that these seas hold life, ESA has started preliminary development
of the Jupiter Icy Moons Explorer (JUICE), a spacecraft proposed for launch around 2022 that would further explore Jupiter and in particular Europa. Recent observations by the Hubble Space
Telescope have uncovered new evidence that Europa, like Saturn's moon Enceladus, has ice venting from its surface. APOD: 2013 December 15
December 2015
Sunday
6
Monday
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Wednesday
Thursday
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Saturday
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Moon near Venus
13
Geminids Meteor Shower
20
14
Geminids Meteor Shower
21
Solstice
27
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Saturn's Iapetus: Painted Moon
Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA
Explanation: What has happened to Saturn's moon Iapetus? Vast sections of this strange world are dark as coal, while others are as bright as ice. The composition of the dark material is unknown, but
infrared spectra indicate that it possibly contains some dark form of carbon. Iapetus also has an unusual equatorial ridge that makes it appear like a walnut. To help better understand this seemingly
painted moon, NASA directed the robotic Cassini spacecraft orbiting Saturn to swoop within 2,000 kilometers in 2007. Pictured above, from about 75,000 kilometers out, Cassini's trajectory allowed
unprecedented imaging of the hemisphere of Iapetus that is always trailing. A huge impact crater seen in the south spans a tremendous 450 kilometers and appears superposed on an older crater of
similar size. The dark material is seen increasingly coating the easternmost part of Iapetus, darkening craters and highlands alike. Close inspection indicates that the dark coating typically faces the moon's
equator and is less than a meter thick. A leading hypothesis is that the dark material is mostly dirt leftover when relatively warm but dirty ice sublimates. An initial coating of dark material may have been
effectively painted on by the accretion of meteor-liberated debris from other moons. This and other images from Cassini's Iapetus flyby are being studied for even greater clues. Image Credit: Cassini
Imaging Team, SSI, JPL, ESA, NASA. APOD: 2012 January 13 .
2016
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