Pluto
Pluto
PLUTO Some of the features already identified in today's New Horizons image
[Many marks on the image of Pluto follow:]
Candy shell Frontal bone Grease stains Bugs JPEG plumes Full text of the wikipedia article on pareidolia Bullet holes New Netherlands Disputed territory Snake pit Tadpole Pluto dinosaur extinction crater Kuiper beltloops Serenity Ghost Dinosaur The good part Moon bud Scars from predator attacks Reset button Megaman Charging socket Cracks (beginning to hatch) Plug (inflating/deflating) Heart Mount Mons Coronary artery disease Debate hole Where we're putting all the people still arguing about Pluto's planet status Chocolate frosting Probably benign Vanilla frosting Dock connector Border of pride lands Hyena country Area missed during ironing
Image credit: NASA/JHUAPL/SwRI - click for original

This comic was posted on Tuesday, July 14, 2015, in honor of the New Horizons deep space probe making its flyby at Pluto , thus breaking the typical Monday/Wednesday/Friday cycle for the xkcd comics. Also on this day he released the first what if? in over three months, and it was called New Horizons . Luckily it did not end up back on Earth, as depicted in 1532: New Horizons , released 1½ month before closest approach.
Randall has taken one of the probe's images of Pluto, and outlined humorous examples of pareidolia on top of it.
It can be compared to preliminary descriptions by geologists, e.g. New Horizons' best look at Pluto before close approach|The Planetary Society .
The comic probably winks at Percival Lowell whose observatory photographed Pluto in 1915 "known" as Planet X. Unfortunately Percival Lowell is most famous for his drawings of the Canals on Mars which are widely misunderstood as channels based on wrong translations from Italian to other languages.
The title text refers to the debate as to whether Pluto should be classified as a full or dwarf planet. This debate was particularly brought into the public eye and came to be seen as a matter of controversy, following the 2006 IAU definition of planet . The text may imagine that this debate winds on, with definitions being created and revised until a ridiculous state is reached whereby Pluto has a special class of celestial body named after it called a 'Pluto' but fails to fulfill the arbitrary criteria set up for it, and hence is called a 'dwarf Pluto'. There actually exist the terms Plutoid and Plutino , that relate directly to groups that Pluto belongs to, but see those pages for details of their use and usage. There has been a real naming conflict whilst generating those two categories, where Plutons was the name chosen initially, whereas Pluton is the usual name of Pluto in some languages.
Candy shell
Suggests Pluto is a confection, like Minmus . May also be a reference to the Mars candy bar.
JPEG plumes
The JPEG image format has the common issue of slightly distorting an image with Compression artifacts . The artifacts shown here do not appear in the official version of this image, but all data sent from New Horizons is compressed and artifacts are common — the full resolution images will be submitted to earth over the next 16 months. There have been tweets about people seeing plumes associated with active volcanoes and the like, which were explained as being artifacts.
Frontal bone
Interpreting Pluto as a head, the frontal bone could be the light-colored region next to the darker top, just above the north pole facing to us.
Grease stains
The area above Pluto's north pole is attributed to grease.
Bugs
Could refer to possible extraterrestrial life on Pluto in the form of insects , or "bugs". In the animated TV series Roughnecks: Starship Troopers Chronicles , an adaptation of Robert Heinlein's novel Starship Troopers , the first battles with the alien "Bugs" took place on Pluto. Maybe it also refers to a software bug at the probe.
Bullet holes
A string of small round features which Randall suggests was the result of Pluto getting shot repeatedly, probably by meteorites.
New Netherlands
Reference to the what if?, Drain the Oceans: Part II , about draining the Earth's oceans onto Mars. In the previous what if?, Drain the Oceans , the Netherlands took over the Earth once their problem with the risk of flooding disappeared. And then they continued to issue forth from the portal that drained the oceans on Earth pouring them onto Mars, to claim Mars as New Netherlands. Presumably, something similar happened on Pluto. This was already again references in both an entry in the table and in the title text of 1555: Exoplanet Names 2 .
Disputed territory
Since the base photograph is identified as "today's New Horizons image," this indicates that a section of Pluto has immediately become the subject of some controversy, possibly a territorial claim or one of several references to the fact that Pluto was demoted from full planet status in 2006.
Snake pit
A generic map hazard.
Full text of the Wikipedia article on pareidolia
Pareidolia is the human brain's tendency to see patterns where they don't exist. While probably a reference to Pluto's heart, the joke is also recursive: You'd be seeing the text of a Wikipedia article explaining to you that you couldn't actually be seeing the text of a Wikipedia article.
Tadpole
One of a number of pareidolic features Randall has outlined.
Kuiper Belt loops
The Kuiper belt is a region in our solar system that contains an unknown amount of icy bodies, one known is Pluto. Randall jokingly refers to Kuiper Belt as the same kind of belt that's used to fasten clothing and identifies features on Pluto's surface as loops for the belt.
Serenity
An outline of the Firefly -class spaceship Serenity , which was the titular vessel from the 2002 TV series Firefly . One of a number of pareidolic features Randall has outlined.
Dinosaur
Nobody can see a dinosaur unless Randall did do this painting on Pluto's surface. And a complex comic needs at least one dinosaur.
The good part
A section of Pluto that is objectively better than the rest.
Moon bud
This could be interpreted as a moon growing/emerging out of Pluto, as a bud is "a compact knob-like growth". A round growth is seen at the location marked, resembling a small, emerging moon.
Ghost
A reference to the classic video game Pacman , wherein the primary antagonists are one of four Ghosts. The Ghost on Pluto appears to have a mouth, however, unlike most depictions of the Pacman Ghosts. One of a number of pareidolic features Randall has outlined.
Pluto dinosaur extinction crater
Suggests Pluto had dinosaurs and lost them the same way Earth did.
Heart
One of a number of pareidolic features Randall has outlined, and the only one (currently) also informally named as such by NASA.
Coronary artery disease
Also known as ischemic heart disease , which causes degradation of heart tissue.  The region identified in the comic looks less 'healthy' (is darker and more ragged) compared to the rest of the 'Heart', which Randall suggests is caused by the disease.
Mount Mons
Referring to the general practice of naming extraterrestrial mountains "X Mons" (e.g. Olympus Mons , a mountain on Mars and the largest mountain in the Solar System), as well as naming terrestrial mountains "Mount X". Since "mons" is Latin for "mountain", the feature's suggested name translates as "Mount Mountain".
Charging socket
A terrain feature suitable for connecting an outside source of electricity for the benefit of implied internal batteries. Compare "dock connector," below.
Cracks (beginning to hatch)
Implying that Pluto is some manner of a giant egg. Possibly a reference to the Doctor Who episode Kill the Moon , in which the Moon is revealed to be an egg from which a monster is hatching. A 2014 article from The Onion , "Moon Finally Hatches," makes the same joke. Also possibly a reference to The Light Fantastic , a Discworld novel in which similar objects are revealed to be the eggs of the world turtle. A similar idea appeared in Jack Williamson's 1934 short story "Born of the Sun".
Plug (inflating/deflating)
Inflatable balls often have a "plug" or opening to insert a needle to inflate or deflate them.
Scars from predator attacks
Since it's all-caps, we can't tell if "PREDATOR" is a proper noun, but this is possibly a reference to the movie series Predator , about a race of aliens who hunt other beings for sport. Alternatively, a planetary predator (such as comic book villain Galactus ) may have previously scarred Pluto.
Reset button
The structure indicated is a small black dot (at least at this distance this picture was taken). Reset buttons on home electronics are often small buttons or holes used to reset the software of the electronic device.
Megaman
One of a number of pareidolic features Randall has outlined, this one in the shape of a popular video game protagonist.
Debate Hole - Where we're putting all the people still arguing about Pluto's planet status
Pluto was reclassified as a dwarf planet rather than a planet following the latter term's controversial redefinition in 2006 by the International Astronomical Union .  Arguments about the classification continue to pop up. The same argument is referenced in the title text. The name implies a proposal to put all the people still arguing about it in this hole on Pluto. This proposal further implies that the continued debate is very annoying by 2015, except perhaps to the debaters themselves.
Area missed during ironing
The area indicated is near the terminator and shows some intriguing topographic relief.
Probably Benign
A neoplasm or tumor is an abnormal growth of tissue. Randall is suggesting that the abnormal region near the heart has been evaluated by a doctor and determined to be benign .
Chocolate frosting
Suggests the discrepancy in color over Pluto's surface may be a function of what cake frosting was used where. This area is the "dark spot" at the head of the "whale" ( http://www.nytimes.com/interactive/2015/07/14/science/space/pluto-flyby.html ).  The so-called "whale's tail" ( http://www.nbcnews.com/science/space/find-heart-whale-new-horizons-picture-pluto-n388816 ), is on the other hemisphere and is not visible in this image, it lies east about 90 degrees from the chocolate frosting/dark spot here.
Vanilla frosting
As above, suggests the discrepancy in color over Pluto's surface may be a function of what cake frosting was used where.
Border of pride lands
A reference to the Disney animated feature The Lion King. In the movie, the Pridelands is the bright and prosperous region ruled by the Lion King while a dark territory beyond its border is controlled by hyenas.
Hyena country
A continuation of the Lion King reference above.
Dock connector
From the point of view of the photograph, this feature of Pluto is at the planet's "bottom," where iPod dock connectors are. Compare "charging socket," above.
PLUTO Some of the features already identified in today's New Horizons image
[Many marks on the image of Pluto follow:]
Candy shell Frontal bone Grease stains Bugs JPEG plumes Full text of the wikipedia article on pareidolia Bullet holes New Netherlands Disputed territory Snake pit Tadpole Pluto dinosaur extinction crater Kuiper beltloops Serenity Ghost Dinosaur The good part Moon bud Scars from predator attacks Reset button Megaman Charging socket Cracks (beginning to hatch) Plug (inflating/deflating) Heart Mount Mons Coronary artery disease Debate hole Where we're putting all the people still arguing about Pluto's planet status Chocolate frosting Probably benign Vanilla frosting Dock connector Border of pride lands Hyena country Area missed during ironing
Image credit: NASA/JHUAPL/SwRI - click for original
