How Do We Colonize Mercury?

Welcome back to the first in our series on Colonizing the Solar System! First up, we take a look at that hot, hellish place located closest to the Sun – the planet Mercury!

Humanity has long dreamed of establishing itself on other worlds, even before we started going into space. We’ve talked about colonizing the Moon, Mars, and even establishing ourselves on exoplanets in distant star systems. But what about the other planets in our own backyard? When it comes to the Solar System, there is a lot of potential real estate out there that we don’t really consider.

Well consider Mercury. While most people wouldn’t suspect it, the closest planet to our Sun is actually a potential candidate for settlement. Whereas it experiences extremes in temperature – gravitating between heat that could instantly cook a human being to cold that could flash-freeze flesh in seconds – it actually has potential as a starter colony.

Examples in Fiction:

The idea of colonizing Mercury been explored by science fiction writers for almost a century. However, it has only been since the the mid-20th century that colonization has been dealt with in a scientific fashion. Some of the earliest known examples of this include the short stories of Leigh Brackett and Isaac Asimov during the 1940s and 50s.

In the former’s work, Mercury is a tidally-locked planet (which was what astronomers believed at the time) that has a “Twilight Belt” characterized by extremes in heat, cold, and solar storms. Some of Asimov’s early work included short stories where a similarly tidally-locked Mercury was the setting, or characters came from a colony located on the planet.

Mercury, as imaged by the MESSENGER spacecraft, revealing parts of the never seen by human eyes. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Mercury, as imaged by the MESSENGER spacecraft, revealing parts of the never seen by human eyes. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

These included “Runaround” (written in 1942, and later included in I, Robot), which centers on a robot that is specifically designed to cope with the intense radiation of Mercury. In Asimov’s murder-mystery story “The Dying Night” (1956) – in which the three suspects hail from Mercury, the Moon and Ceres – the conditions of each location are key to finding out who the murderer is.

In 1946, Ray Bradbury published “Frost and Fire”, a short story that takes place on a planet described as being next to the sun. The conditions on this world allude to Mercury, where the days are extremely hot, the nights extremely cold, and humans live for only eight days. Arthur C. Clarke’s Islands in the Sky (1952) contains a description of a creature that lives on what was believed at the time to Mercury’s permanently dark side and occasionally visits the twilight region.

In his later novel, Rendezvous with Rama (1973), Clarke describes a colonized Solar System which includes the Hermians, a toughened branch of humanity that lives on Mercury and thrives off the export of metals and energy. The same setting and planetary identities is used in his 1976 novel Imperial Earth.

In Kurt Vonnegut’s novel The Sirens of Titan (1959), a section of the story is set in caves located on the dark side of the planet. Larry Niven’s short story “The Coldest Place” (1964) teases the reader by presenting a world that is said to be the coldest location in the Solar System, only to reveal that it is the dark side of Mercury (and not Pluto, as is generally assumed).

"Lava Falls on Mercury", cover art by Ken Fagg for If magazine, June 1954
“Lava Falls on Mercury” (by Ken Fagg) for If magazine, June 1954. Credit: Public Domain

Mercury also serves as a location in many of Kim Stanley Robinson’s novels and short stories. These include The Memory of Whiteness (1985), Blue Mars (1996), and 2312 (2012), in which Mercury is the home to a vast city called Terminator. To avoid the harmful radiation and heat, the city rolls around the planet’s equator on tracks, keeping pace with the planet’s rotation so that it stays ahead of the Sun.

In 2005, Ben Bova published Mercury (part of his Grand Tour series) that deals with the exploration of Mercury and colonizing it for the sake of harnessing solar energy. Charles Stross’ 2008 novel Saturn’s Children involves a similar concept to Robinson’s 2312, where a city called Terminator traverses the surface on rails, keeping pace with the planet’s rotation.

Proposed Methods:

A number of possibilities exist for a colony on Mercury, owing to its the nature of its rotation, orbit, composition and geological history. For example, Mercury’s slow rotational period means that one side of the planet is facing towards the Sun for extended periods of time – reaching temperatures highs of up to 427 °C (800 °F) – while the side facing away experiences extreme cold (-193 °C; -315 °F).

In addition, the planet’s rapid orbital period of 88 days, combined with its sidereal rotation period of 58.6 days, means that it takes roughly 176 Earth days for the Sun to return to the same place in the sky (i.e. a solar day). Essentially, this means that a single day on Mercury lasts as long as two of its years. So if a city were placed on the night-side, and had tracks wheels so it could keep moving to stay ahead of the Sun, people could live without fear of burning up.

Images of Mercury's northern polar region, provided by MESSENGER. Credit: NASA/JPL
Images of Mercury’s northern polar region, provided by MESSENGER. Credit: NASA/JPL

In addition, Mercury’s very low axial tilt (0.034°) means that its polar regions are permanently shaded and cold enough to contain water ice. In the northern region, a number of craters were observed by NASA’s MESSENGER probe in 2012 which confirmed the existence of water ice and organic molecules. Scientists believe that Mercury’s southern pole may also have ice, and claim that an estimated 100 billion to 1 trillion tons of water ice could exist at both poles, which could be up to 20 meters thick in places.

In these regions, a colony could be built using a process called “paraterraforming” – a concept invented by British mathematician Richard Taylor in 1992. In a paper titled “Paraterraforming – The Worldhouse Concept”, Taylor described how a pressurized enclosure could be placed over the usable area of a planet to create a self-contained atmosphere. Over time, the ecology inside this dome could be altered to meet human needs.

In the case of Mercury, this would include pumping in a breathable atmosphere, and then melting the ice to create water vapor and natural irrigation. Eventually, the region inside the dome would become a livable habitat, complete with its own water cycle and carbon cycle. Alternately, the water could be evaporated, and oxygen gas created by subjecting it to solar radiation (a process known as photolysis).

Another possibility would be to build underground. For years, NASA has been toying with the idea of building colonies in stable, underground lava tubes that are known to exist on the Moon. And geological data obtained by the MESSENGER probe during flybys it conducted between 2008 and 2012 led to speculation that stable lava tubes might exist on Mercury as well.

A previous MESSENGER image of hollows inside Tyagaraja crater
A previous MESSENGER image of hollows inside Tyagaraja crater. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

This includes information obtained during the probe’s 2009 flyby of Mercury, which revealed that the planet was a lot more geologically active in the past than previously thought. In addition, MESSENGER began spotting strange Swiss cheese-like features on the surface in 2011. These holes, which are known as “hollows”, could be an indication that underground tubes exist on Mercury as well.

Colonies built inside stable lava tubes would be naturally shielded to cosmic and solar radiation, extremes in temperature, and could be pressurized to create breathable atmospheres. In addition, at this depth, Mercury experiences far less in the way of temperature variations and would be warm enough to be habitable.

Potential Benefits:

At a glance, Mercury looks similar to the Earth’s Moon, so settling it would rely on many of the same strategies for establishing a moon base. It also has abundant minerals to offer, which could help move humanity towards a post-scarcity economy. Like Earth, it is a terrestrial planet, which means it is made up of silicate rocks and metals that are differentiated between a iron core and silicate crust and mantle.

However, Mercury is composed of 70% metals whereas’ Earth’s composition is 40% metal. What’s more, Mercury has a particular large core of iron and nickel, and which accounts for 42% of its volume. By comparison, Earth’s core accounts for only 17% of its volume. As a result, if Mercury were to be mined, enough minerals could be produced to last humanity indefinitely.

The different colors in this MESSENGER image of Mercury indicate the chemical, mineralogical, and physical differences between the rocks that make up the planet’s surface. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.
The different colors in this MESSENGER image of Mercury indicate the planet’s chemical, mineralogical, and physical differences. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.

Its proximity to the Sun also means that it could harness a tremendous amount of energy. This could be gathered by orbital solar arrays, which would be able to harness energy constantly and beam it to the surface. This energy could then be beamed to other planets in the Solar System using a series of transfer stations positioned at Lagrange Points.

Also, there’s the matter of Mercury’s gravity, which is 38% percent of Earth normal. This is over twice what the Moon experiences, which means colonists would have an easier time adjusting to it. At the same time, it is also low enough to present benefits as far as exporting minerals is concerned, since ships departing from its surface would need less energy to achieve escape velocity.

Lastly, there is the distance to Mercury itself. At an average distance of about 93 million km (58 million mi), Mercury ranges between being 77.3 million km (48 million mi) to 222 million km (138 million mi) away from the Earth. This puts it a lot closer than other possible resource-rich areas like the Asteroid Belt (329 – 478 million km distant), Jupiter and its system of moons (628.7 – 928 million km), or Saturn’s (1.2 – 1.67 billion km).

Also, Mercury achieves an inferior conjunction – the point where it is at its closest point to Earth – every 116 days, which is significantly shorter than either Venus’ or Mars’. Basically, missions destined for Mercury could launch almost every four months, whereas launch windows to Venus and Mars would have to take place every 1.6 years and 26 months, respectively.

The MESSENGER spacecraft has been in orbit around Mercury since March 2011 – but its days are numbered. Image credit: NASA/JHUAPL/Carnegie Institution of Washington
The MESSENGER spacecraft has been in orbit around Mercury since March 2011 – but its days are numbered. Credit: NASA/JHUAPL/Carnegie Institution of Washington

In terms of travel time, several missions have been mounted to Mercury that can give us a ballpark estimate of how long it might takes. For instance, the first spacecraft to travel to Mercury, NASA’s Mariner 10 spacecraft (which launched in 1973), took about 147 days to get there.

More recently, NASA’s MESSENGER spacecraft launched on August 3th, 2004 to study Mercury in orbit, and made its first flyby on January 14th, 2008. That’s a total of 1,260 days to get from Earth to Mercury. The extended travel time was due to engineers seeking to place the probe in orbit around the planet, so it needed to proceed at a slower velocity.

Challenges:

Of course, a colony on Mercury would still be a huge challenge, both economically and technologically. The cost of establishing a colony anywhere on the planet would be tremendous, and would require abundant materials to be shipped from Earth, or mined on site. Either way, such an operation would require a large fleet of spaceships capable of making the journey in a respectable amount of time.

Such a fleet does not yet exist, and the cost of developing it (and the associated infrastructure for getting all the necessary resources and supplies to Mercury) would be tremendous. Relying on robots and in-situ resource utilization (ISRU) would certainly cut costs and reduce the amount of materials that would need to be shipped. But these robots and their operations would need to be shielded from radiation and solar flares until they got the job done.

Enhanced-color image of Munch, Sander and Poe craters amid volcanic plains (orange) near Caloris Basin NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Enhanced-color image of Munch, Sander and Poe craters amid volcanic plains (orange) near Caloris Basin. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Basically, the situation is like trying to establish a shelter in the middle of a thunderstorm. Once it is complete, you can take shelter. But in the meantime, you’re likely to get wet and dirty! And even once the colony was complete, the colonists themselves would have to deal with the ever-present hazards of radiation exposure, decompression, and extremes in heat and cold.

As such, if a colony were established on Mercury, it would be heavily dependent on its technology (which would have to be rather advanced). Also, until such time as the colony became self-sufficient, those living there would be dependent on supply shipments that would have to come regularly from Earth (again, shipping costs!)

Still, once the necessary technology was developed, and we could figure out a cost-effective way to create one or more settlements and ship to Mercury, we could look forward to having a colony that could provide us with limitless energy and minerals. And we would have a group of human neighbors known as Hermians!

As with everything else pertaining to colonization and terraforming, once we’ve established that it is in fact possible, the only remaining question is “how much are we willing to spend?”

We have written many interesting articles on colonization here at Universe Today. Here’s Why Colonize the Moon First?, Colonizing Venus with Floating Cities, Will We Ever Colonize Mars?, and The Definitive Guide to Terraforming.

Astronomy Cast also has some interesting episodes on the subject. Check out Episode 95: Humans to Mars, Part 2 – Colonists, Episode 115: The Moon, Part 3 – Return to the Moon, Episode 381: Hollowing Asteroids in Science Fiction.

Sources:

  • geoscienceworld.org/content/early/2014/10/14/G35916.1.full.pdf+html?ijkey=rxQlFflgdo/rY&keytype=ref&siteid=gsgeology
  • Taylor, Richard L. S. (1992) Paraterraforming – The worldhouse concept. Journal of the British Interplanetary Society, vol. 45, no. 8
  • Viorel Badescu, Kris Zacny (eds). Inner Solar System: Prospective Energy and Material Resources. Springer, 2015
  • nasa.gov/science-news/science-at-nasa/2011/24oct_sleepyhollows/
  • nasa.gov/centers/goddard/news/features/2010/biggest_crater.html
  • nasa.gov/science-news/science-at-nasa/2011/24oct_sleepyhollows/

 

Mercury MESSENGER Mission Concludes with a Smashing Finale!

The planet Mercury has a brand new 52-foot-wide crater. At 3:26 p.m.  EDT this afternoon, NASA’s MESSENGER spacecraft bit the Mercurial dust, crashing into the planet’s surface at over 8,700 mph just north of the Shakespeare Basin. Because the impact happened out of sight and communication with the Earth, the MESSENGER team had to wait about 30 minutes after the predicted impact to announce the mission’s end. 

NASA estimates that the MESSENGER spacecraft would crash into Mercury this afternoon at 3:26 p.m. EDT near the 30-mile-wide crater Janacek on the opposite side of the planet from Earth. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
NASA predicted that the MESSENGER spacecraft would crash into Mercury this afternoon at 3:26 p.m. EDT near the 30-mile-wide crater Janacek  and the large Shakespeare Basin on the opposite side of the planet from Earth. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Even as MESSENGER faced its demise, it continued to take pictures and gather data right up until impact. The first-ever space probe to orbit the Solar System’s innermost planet, MESSENGER has completed 4,103 orbits as of this morning. Not only has it imaged the planet in great detail, but using it seven science instruments, scientists have gathered data on the composition and structure of Mercury’s crust, its geologic history, the nature of its magnetic field and rarefied sodium-calcium atmosphere, and the makeup of its iron core and icy materials near its poles.

Color-coded view of Carnegie Rupes (ridge) with low elevations in blue and high in red. The ridge formed as the Mercury's interior cooled, resulting in the overall shrinking of the planet. Parts of the landscape lapped over other parts as the planet shrunk. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Color-coded view of Carnegie Rupes at left with low elevations in blue and high in red. The ridge formed as Mercury’s interior cooled, resulting in the overall shrinking of the planet. Parts of the landscape lapped over other parts as the planet shrunk. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Images show those ubiquitous craters but also features that set its moonlike landscape apart from the Moon including volcanic plains, tectonic landforms that indicate the planet shrank as its interior cooled and mysterious mouse-like nibbles called “hollows”, where surface material may be vaporizing in sunlight leaving behind a network of holes. To learn more about the mission’s “greatest hits”, check out its Top Ten discoveries or pay a visit to the Gallery.

The rounded, depressions, called "hollows", are a fascinating discovery of MESSENGER's orbital mission and may have been formed by vaporization of something in the material when exposed by the Raditladi impact. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
The rounded depressions, called “hollows”, are a fascinating discovery of MESSENGER’s orbital mission and may have been formed by vaporization of materials in the surface when exposed by the Raditladi impact. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

MESSENGER mission controllers conducted the last of six planned maneuvers on April 24 to raise the spacecraft’s minimum altitude sufficiently to extend orbital operations and further delay the probe’s inevitable impact onto Mercury’s surface, but it’s now out of propellant. Without the ability to counteract the Sun’s gravity, which is slowly pulling the craft closer to Mercury’s surface, the team prepared for the inevitable.

False color images of Mercury taken with MESSENGER's Mercury Atmosphere and Surface Composition Spectrometer (MASCS) in everything from infrared to ultraviolet light reveal colorful differences in terrain and surface mineralogy. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
False color images of Mercury taken with MESSENGER’s Mercury Atmosphere and Surface Composition Spectrometer (MASCS) in everything from infrared to ultraviolet light reveal colorful differences in terrain and surface mineralogy. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

The spacecraft actually ran out of propellant a while back, but controllers realized they could re-purpose a stock of helium, originally carried to pressurize the fuel, for a few final blasts to keep it alive and doing science right up to the last minute. During its final hours today, MESSENGER will be shooting and sending back as many new pictures as possible the same way you’d squeeze in one last shot of the Grand Canyon before departing for home. It’s also holding hundreds of older photos in its memory chip and will send as many of those as it can before the final deadline.

Farewell MESSENGER! Artist view of the spacecraft orbiting the innermost planet Mercury. Credit: NASA
Farewell MESSENGER! Artist view of the spacecraft in orbit about Mercury. Credit: NASA

“Operating a spacecraft in orbit about Mercury, where the probe is exposed to punishing heat from the Sun and the planet’s dayside surface as well as the harsh radiation environment of the inner heliosphere (Sun’s sphere of influence), would be challenge enough,” said Principal Investigator Sean Solomon, MESSENGER principal investigator. “But MESSENGER’s mission design, navigation, engineering, and spacecraft operations teams have fought off the relentless action of solar gravity, made the most of every usable gram of propellant, and devised novel ways to modify the spacecraft trajectory never before accomplished in deep space.”

Face northwest starting about 45 minutes after sunset to look for Mercury tonight. It will lie about two fists below Venus and only 1.5 from the Pleiades star cluster. Source: Stellarium
Face northwest starting about 45 minutes after sunset to find Mercury tonight. It’s located about two fists to the lower right of Venus and just 1.5° below the Pleiades star cluster. Use binoculars to see the star cluster more easily. Source: Stellarium

Ground-based telescopes won’t be able to spy MESSENGER’s impact crater because of its small size, but the BepiColombo Mercury probe, due to launch in 2017 and arrive in orbit at Mercury in 2024, should be able to get a glimpse. Speaking of spying, you can see the planet Mercury tonight (and for the next week or two), when it will be easily visible low in the northwestern sky starting about 45 minutes after sundown. The planet coincidentally makes its closest approach to the Pleiades star cluster tonight and tomorrow.

Use the occasion to wish MESSENGER a fond farewell.

On the Edge of Tyagaraja

Here’s a rather interesting view from orbit around the innermost planet: Mercury’s Tyagaraja crater, the interior of which is seen here in an oblique-angled image acquired by the MESSENGER spacecraft on November 12, 2011 (and released August 16, 2013.)

This view looks west across the northern portion of the 97-kilometer (60-mile) -wide crater, and shows some of its large central peaks, terraced walls, and bright erosion features called hollows that are spread across a wide swath of its interior.

First seen by MESSENGER in 2011, hollows are thought to indicate an erosion process unique to Mercury because of its composition and close proximity to the Sun. The lack of craters within hollows seems to indicate that they are relatively young features… in fact, they may be part of a process that continues today.

This image was acquired as a high-resolution targeted observation. Targeted observations are images of a small area on Mercury’s surface at resolutions much higher than the 200-meter/pixel morphology base map.

Enhanced-color image of Tyagaraja crater acquired on Sept. 29, 2011. Its large hollow field is highlighted.
Enhanced-color image of Tyagaraja crater acquired on Sept. 29, 2011. Its large hollow field is highlighted.

Tyagaraja is named after Kakarla Tyagabrahmam, an 18th-century composer of classical Indian Carnatic music.

Read more on the MESSENGER website here.

Images: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Mercury Shows Off Its Reds, Whites, and Blues

At first glance, the planet Mercury may bear a striking resemblance to our own Moon. True, both are heavily-cratered, airless worlds that hide pockets of ice inside polar shadows… but there the similarities end. In addition to being compositionally different than the Moon, Mercury also has surface features that you won’t find on the lunar surface — or anywhere else in the Solar System.

The picture above, part of an 11-color targeted image acquired by MESSENGER on April 25, 2013, shows the varied terrain found within the 97-kilometer-wide Tyagaraja crater located near Mercury’s equator. The reds, blues, greens, and oranges, much more saturated than anything we’d see with our own eyes, correspond to surface materials of different compositions… and the brightest spots within the crater are features called “hollows” that are truly unique to Mercury, possibly resulting from the planet’s close interaction with the solar wind.

First noted in September of 2011, hollows have been identified across many areas of Mercury. One hypothesis is that they’re formed by the sublimation of subsurface material exposed inside larger craters. Being so close to the Sun and lacking a protective atmosphere, Mercury is constantly being scoured by the solar wind — a relentless stream of charged particles that’s actively “sandblasting” exposed volatiles from the planet’s surface!

Read more about hollows here.

A previous MESSENGER image of hollows inside Tyagaraja crater
A previous MESSENGER image of hollows inside Tyagaraja crater

The reddish spot at the center of the crater in the top image is likely material surrounding a pyroclastic vent, which appear red and orange in MDIS images. The dark material that appears bluish is something called “low reflectance material” (LRM).

The image was acquired as a targeted high-resolution 11-color image set. Acquiring 11-color targets is a new MESSENGER campaign that began in March and utilizes all of the Wide-Angle Camera’s 11 narrow-band color filters. Because of the large data volume involved, only features of special scientific interest are targeted for imaging in all 11 colors.

Full of geologically interesting features the crater was named for Kakarla Tyagabrahmam, an 18th century composer of classical South Indian music.

The first spacecraft to establish orbit around Mercury in summer 2011, MESSENGER is capable of continuing orbital operations until early 2015.

Read more on the Johns Hopkins University APL MESSENGER site here.

Credits:  NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Evidence for Active Hollows Formation on Mercury

MESSENGER targeted-observation image of the interior of Eminescu crater

A recent image acquired by NASA’s MESSENGER spacecraft shows the interior of Eminescu, a youngish 130-km (80 mile) wide crater just north of Mercury’s equator. Eminescu made science headlines last year with MESSENGER’s discovery of curious eroded blotches called “hollows” scattered across its interior and surrounding its central peak, and now it looks like the spacecraft may have spotted some of these strange features in their earliest stages of formation along the inner edge of the crater’s rim.

First announced in September 2011, hollows have now been identified in many areas across Mercury. They had showed up in previous images as only bright spots, but once MESSENGER established orbit in March 2011 and began its high-resolution imaging of Mercury’s surface it soon became clear that these features were something totally new.

The lack of craters within hollows indicates that they are relatively young. It was suggested that they may be the result of an ongoing process on Mercury — a suggestion supported by this recent image, acquired on November 19, 2012.

In addition to the hollows seen in the smooth central part of the crater and around the base of the central peak, there are also some small bright spots visible within the knobby terrain extending from the base of the crater wall (see detail at right). These bright spots could well be very young hollows, revealing a process in action that is, as far as we know, unique to the planet Mercury.

It’s thought that hollows are formed by the solar wind constantly blasting Mercury’s surface, scouring away deposits of volatile materials in its crust that have been left exposed by impacts.

The image above shows an area about 42 km across. Read more on the MESSENGER mission site here.

 Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

 

Warhol Crater Gets Its 15 Minutes of Fame

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As pop art icon Andy Warhol said, “In the future everyone will be famous for fifteen minutes,”  and so here’s an image of the crater on Mercury that now bears his name, set up in the style of one of his multicolored silkscreens.

Warhol is one of 23 craters on Mercury to be recently approved for names by the International Astronomical Union (IAU), joining other notable artists, authors and musicians like Gustav Holst, Rene Magritte and Dr. Seuss who now have craters named in their honor on the first rock from the Sun.

95 km (59 miles) in diameter, Warhol crater features a large, elongated central peak, stepped walls and many of the curious erosions known as hollows.

The original image, seen at top left, was acquired by NASA’s MESSENGER spacecraft on October 21, 2011, using its Wide-Angle Camera Mercury Dual Imaging System (MDIS) instrument.

With the new list of 23 named craters, there are now 76 officially (and artistically) titled craters on Mercury since MESSENGER’s first pass of the planet in January 2008.

See the original release by the MESSENGER mission team here.

“I’m bored with that line. I never use it anymore. My new line is “In 15 minutes everybody will be famous.”
– Andy Warhol (1928 – 1987)

Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Bright Peaks, Dark Shadows

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The 68-mile (109-km) -wide Amaral crater on Mercury reveals its brightly-tipped central peaks in this image, acquired by NASA’s MESSENGER spacecraft on Feb. 4, 2012. Long shadows are cast by the crater’s peaks and rugged rim (north is to the left.)

The image was acquired as a high-resolution targeted observation with MESSENGER’s Narrow-Angle Camera (NAC) on its Mercury Dual Imaging System (MDIS).

Amaral’s bright peaks were first spotted during MESSENGER’s first flyby of Mercury in Jan. 2008. With a smooth floor, visible ejecta and small secondary craters, Amaral appeared noticeably younger than the heavily cratered surface around it.

Amaral's "blue" peaks seen in a color-enhanced global image acquired Jan. 14, 2008.

Its central peaks also attracted astronomers’ interest, as they were seen to possess a striking blue hue in color-enhanced images that likely indicates rocks with different composition from the surrounding surface.

Amaral’s peaks resemble those of the slightly larger crater Eminescu, which is now known to contain recently-discovered features called hollows. It’s not yet known if Amaral also contains hollows, but it’s suspected that they may be present on the tips of the peaks.

The crater is named after Brazilian artist Tarsila do Amaral. She lived from 1886 to 1973 and is considered to be one of the leading Latin American modernist painters.

Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.

More “Hollowed Ground” on Mercury

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The latest featured image from NASA’s MESSENGER spacecraft, soon to complete its first year in orbit around Mercury, shows the central peak of the 78-mile (138-km) – wide crater Eminescu surrounded by more of those brightly-colored surface features dubbed “hollows”. Actually tinted a light blue color, hollows may be signs of an erosion process unique to Mercury because of its composition and close proximity to the Sun.

First noted in September of last year, hollows have now been identified in many areas across Mercury. They showed up in previous images as only bright spots, but once MESSENGER established orbit in March of 2011 and began high-resolution imaging of Mercury’s surface it became clear that these features were something totally new.

The lack of craters within hollows seems to indicate that they are relatively young features. In fact, they may be part of a process that continues even now.

“Analysis of the images and estimates of the rate at which the hollows may be growing led to the conclusion that they could be actively forming today,” said David Blewett of the Johns Hopkins University Applied Physics Laboratory (APL).

One hypothesis is that the hollows are formed by the sublimation of subsurface material exposed during the creation of craters, around which they are most commonly seen. Being so close to the Sun (29 million miles/46 million km at closest) and lacking a protective atmosphere like Earth’s, Mercury is constantly being scoured by the powerful solar wind. This relentless stream of charged particles may literally be “sandblasting” exposed volatile materials off the planet’s surface!

The image above shows an area approximately 41 miles (66 km) across. It has been rotated to enhance perspective; see the original image and caption here.

Image: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington