Recent images sent by NASA's New Horizons spacecraft show possible clouds floating over the frozen landscape including the streaky patch at right. Credit: NASA/JHUAPL/SwR
Recent images sent by NASA’s New Horizons spacecraft show possible clouds floating over the frozen landscape including the hazy streak right of center. Credit: NASA/JHUAPL/SwRI
I think we were all blown away when the New Horizons spacecraft looked back at Pluto’s dark side and returned the first photos of a surprisingly complex, layered atmosphere. Colorless nitrogen along with a small percentage of methane make up Pluto’s air. Layers of haze are likely created when the two gases react in sunlight to form tiny, soot-like particles called tholins. These can ultimately grow large enough to settle toward the surface and coat and color Pluto’s icy exterior.
Close up of the back side of Pluto taken by New Horizons shows multiple layers of haze in its mostly nitrogen atmosphere. Credit: NASA/JHUAPL/SwRI
Now it seems Pluto’s atmosphere is capable of doing even more — making clouds! In an e-mail exchange with New Scientist, Lowell Observatory astronomer Will Grundy discusses the possibility that streaks and small condensations within the hazes might be individual clouds. Grundy also tracked a feature as it passed over different parts of the Plutonian landscape below, strongly suggesting a cloud. If confirmed, they’d be the first-ever clouds seen on the dwarf planet, and a sign this small 1,473-mile-wide (2,370 km) orb possesses an even more complex atmosphere than imagined.
Faint arrows along Pluto’s limb point to possible clouds in a low altitude haze layer. More distinct possible clouds are arrowed at left. Credit: NASA/JHUAPL/SwRI15 minutes after its closest approach, New Horizons snapped this image of the smooth expanse of Sputnik Planum (right) flanked to the west (left) by rugged mountains up to 11,000 feet (3,500 meters) high, including the informally named Norgay Montes in the foreground and Hillary Montes on the skyline. The backlighting highlights more than a dozen layers of haze in Pluto’s tenuous but distended atmosphere. Credit: NASA/JHUAPL/SwRI
Given the onion-like layers of haze and potential clouds, perhaps we shouldn’t be surprise that it snows on Pluto. The New Horizons team announced the discovery this week of a chain of exotic snowcapped mountains stretching across the dark expanse of the informally named Cthulhu Regio. Cthulhu, pronounced kuh-THU-lu and named for a character in American horror writer H.P. Lovecraft’s books, stretches nearly halfway around Pluto’s equator, starting from the west of the vast nitrogen ice plain, Sputnik Planum. At 1,850 miles (3,000 km) long and 450 miles (750 km) wide, Cthulhu is a bit larger than the state of Alaska. But ever so much colder!
The upper slopes of Cthulhu’s highest peaks are coated with a bright material that contrasts sharply with the dark red color of the surrounding plains. Scientists think it’s methane ice condensed from Pluto’s atmosphere. The far right panel shows the distribution of methane ice on the surface. Credit: NASA/JHUAPL/SwRI
Cthulhu’s red color probably comes from a covering of dark tholins formed when methane interacts with sunlight. But new close-up images reveal that the region’s highest mountains appear coated with a much brighter material. Scientists think it’s methane, condensed as ice onto the peaks from Pluto’s atmosphere.
“That this material coats only the upper slopes of the peaks suggests methane ice may act like water in Earth’s atmosphere, condensing as frost at high altitude,” said John Stansberry, a New Horizons science team member.
Compositional data from the New Horizon’s Ralph/Multispectral Visible Imaging Camera (MVIC), shown in the right panel in the image above, shows that the location of the bright ice on the mountain peaks correlates almost exactly with the distribution of methane ice, shown in false color as purple.
New Horizons still has plenty of images stored on its hard drive, so we’re likely to see more clouds, frosty peaks and gosh-knows-what-else as the probe speeds ever deeper into space while returning daily postcards from its historic encounter.
This enhanced color view Long canyons run vertically across the polar area—part of the informally named Lowell Regio, named for Percival Lowell, who founded Lowell Observatory and initiated the search that led to Pluto’s discovery. The widest of the canyons is about 45 miles (75 kilometers) wide and runs close to the north pole. Roughly parallel subsidiary canyons to the east and west are approximately 6 miles (10 kilometers) wide.
This enhanced color view shows long canyons running vertically across Pluto’s north polar region — part of the informally named Lowell Regio, named for Percival Lowell, who founded Lowell Observatory and initiated the search that led to Pluto’s discovery. The widest of the canyons is about 45 miles (75 km) wide and runs close to the north pole. Roughly parallel secondary canyons to the east and west are approximately 6 miles (10 km) wide. Click for a hi-res view. Credit: NASA/JHUAPL/SRI
Pluto’s frozen nitrogen custard “heart” has certainly received its share of attention. Dozens of wide and close-up photos homing on this fascinating region rimmed by mountains and badlands have been relayed back to Earth by NASA’s New Horizons probe after last July’s flyby. For being only 1,473 miles (2,370 km) in diameter, Pluto displays an incredible diversity of landscapes.
Annotated version showing sinuous valleys, canyons and depressions and irregular-shaped pits. Credit: NASA/JHUAPL/SRI with additional annotations by the author
This week, the New Horizons team shifted its focus northward, re-releasing an enhanced color image of the north polar area that was originally part of a high-resolution full-disk photograph of Pluto. Inside of the widest canyon, you can trace the sinuous outline of a narrower valley similar in outward appearance to the Moon’s Alpine Valley, cut by a narrow, curvy rill that once served as a conduit for lava.
A composite of enhanced color images of Pluto (lower right) and Charon, taken by NASA’s New Horizons spacecraft on July 14, 2015. This image highlights the striking differences between Pluto and Charon. The color and brightness of both Pluto and Charon have been processed identically to allow direct comparison of their surface properties, and to highlight the similarity between Charon’s polar red terrain and Pluto’s equatorial red terrain. Pluto and Charon are shown with approximately correct relative sizes, but their separation is not to scale. Credit: NASA/JHUAPL/SRI
We see multiple canyons in Pluto’s polar region, their walls broken and degraded compared to canyons seen elsewhere on the planet. Signs that they may be older and made of weaker materials and likely formed in ancient times when Pluto was more tectonically active. Perhaps they’re related to that long-ago dance between Pluto and its largest moon Charon as the two transitioned into their current tidally-locked embrace.
Cropped version with arrows pointing to three, odd-shaped pits that may reflect sinking of Pluto’s crust. Credit: NASA/JHUAPL/SRI
In the lower right corner of the image, check out those funky-shaped pits that resemble the melting outlines of boot prints in the snow. They reach 45 miles (70 km) across and 2.5 miles (4 km) deep and may indicate locations where subsurface ice has melted or sublimated (vaporized) from below, causing the ground to collapse.
Notice the variation in color across the landscape from yellow-orange to pale blue. High elevations show up in a distinctive yellow, not seen elsewhere on Pluto, with lower elevations and latitudes a bluish gray. New Horizons’ infrared measurements show abundant methane ice across the Lowell Region, with relatively little nitrogen ice. The yellow terrains may be older methane deposits that have been more processed by solar UV light than the bluer terrain. The color variations are especially striking in the area of the collapse pits.
The new map shows exposed water ice at Pluto to be considerably more widespread across its surface than was previously known. Its greatest concentration lies in the red-hued regions (in visual light) to the west of Tombaugh Regio, the large, heart-shaped feature. Credit: NASA/JHUAPL/SRI
Pluto’s icy riches include not only methane and nitrogen but also water, which forms the planet’s bedrock. NASA poetically refers to the water ice as “the canvas on which (Pluto’s) more volatile ices paint their seasonally changing patterns”. Recent images made in infrared light shows little or no water ice in the informally named places called Sputnik Planum (the left or western region of Pluto’s “heart”) and Lowell Regio. This indicates that at least in these regions, Pluto’s bedrock remains well hidden beneath a thick blanket of other ices such as methane, nitrogen and carbon monoxide.
To delve more deeply into Pluto, visit the NASA’s photojournal archive, where you’ll find 130 photos (and counting!) of the dwarf planet and its satellites.
Whenever I go to the post office to pick up stamps I always ask for the most colorful ones. No dead president heads for me. Mailing letters is a rare thing nowadays — might as well choose something colorful and interesting. How sweet then that we’ll soon be able to pick and stick our favorite planets (and dwarf planet!) on the mail and send them flying off to far places.
The U.S. Postal Service sneak-previewed a new series of stamps earlier this year highlighting NASA’s Planetary Science program, including a do-over of a famous Pluto stamp commemorating the New Horizons’ historic 2015 flyby. Also in the works are eight new colorful Forever stamps featuring NASA images of the planets, a Global Forever stamp dedicated to Earth’s moon and a tribute to 50 years of Star Trek.
New Horizons Principal Investigator Alan Stern (left), Johns Hopkins University Applied Physics Laboratory (APL) Director Ralph Semmel (center) and New Horizons Co-Investigator Will Grundy Lowell Observatory hold a print of an U.S. stamp with their suggested update since the New Horizons spacecraft has explored Pluto last July. Credit: NASA/Bill Ingalls
The New Horizons team, which placed a 29-cent 1991 “Pluto: Not Yet Explored” stamp on board the New Horizons spacecraft, is thrilled at the updated stamp recognizing the mission.
“The New Horizons project is proud to have such an important honor from the U.S. Postal Service,” said Alan Stern, New Horizons principal investigator from the Southwest Research Institute. “Since the early 1990s the old, ‘Pluto Not Explored’ stamp served as a rallying cry for many who wanted to mount this historic mission of space exploration. Now that NASA’s New Horizons has accomplished that goal, it’s a wonderful feeling to see these new stamps join others commemorating first explorations of the planets.”
In the upcoming planet series, we’re treated to a color-enhanced Mercury taken by MESSENGER highlighting the planet’s varied terrains. Venus appears in all its naked volcanic glory courtesy of the Magellan probe which mapped the planet using cloud-penetrating radar. Like Mercury, it’s also color-enhanced since it’s impossible to see the surface in visual light even from orbit. Earth and Mars were photographed in natural light with orbiting satellites in tow.
The Hubble Space Telescope photographed Jupiter in infrared light in 2004, capturing a rare triple transit of the moons Ganymede, Io and Callisto. Saturn comes to us from the Cassini probe, still in good health and routinely sending gorgeous images every month of the ringed planet and its moons. Pity the rings had to be trimmed, but it had to be done to keep all the globes close to the same relative size. Hubble took Uranus’ picture in infrared light, while the Neptune close-up was sent by the Voyager 2 spacecraft in 1989.
2016 also marks the 50th anniversary of the television premier of StarTrek, which the post office will commemorate with the new Star Trek Forever stamps. They feature four digital illustrations inspired by the television program: the Starship Enterprise inside the outline of a Starfleet insignia, the silhouette of a crewman in a transporter, the silhouette of the Enterprise from above and the Enterprise inside the outline of the Vulcan salute.
The Global Moon stamp was issued on Feb. 22. You can pre-order the Pluto and planet stamps from USPS.com 30 days before their dedication between May 28 and June 4 at the World Stamp Show in New York. Expect the Star Trek series sometime this summer.
Mars has a lot of heart (s)! Send one to your Valentine Credit: NASA
Happy Valentine’s Day from the Pluto New Horizon’s mission! Click to download a high resolution pdf file you can print out. Credit: NASA
Still looking for the right card for your sweetheart this Valentine’s Day? Why not do it in cosmic proportion by getting NASA on your side? The tender-hearted folks at agency may have just what you’re looking for.
The staff at the New Horizons mission headquarters offers two valentines this season that play off Pluto’s heart-shaped, icy plain Tombaugh Regio. While the temperature there hovers around 400 below, you’re guaranteed a 98.6° smile when your sweetie opens the card and sees your love reflected in glittering nitrogen ice.
Mars has a lot of heart (s)! Click to select and send your Valentine a Red Planet-themed e-card. Credit: NASA
Pluto not your thing? Select from 12 different Mars e-card love greetings at this NASA site and blow your partner away in a Martian dust devil of love. Many of the heart-shaped features depicted on the cards are genuine features and include collapse pits, craters and mesas.
Click to pick from 8 different valentines at the OSIRIS-Rex asteroid mission site. Credit: NASA
Even the asteroids send their saucy wishes. Check out the delightful series of valentines from the upcoming OSIRIS-Rex sample return mission to 101955 Bennu, slated to launch in September this year and return a sample of the carbonaceousasteroid to Earth in 2023. If you go this route, I’d complement the card with a meal heavy on edible carbonaceous material at your partner’s favorite restaurant.
Happy Valentine’s Day! Spread the love for a happier planet.
NASA releases budget request for Fiscal Year 2017. Credit: NASA
NASA releases budget request for Fiscal Year 2017. Credit: NASA
The Obama Administration has announced its new Federal budget and is proposing to cut NASA’s Fiscal Year 2017 Budget to $19 billion by carving away significant funding for deep space exploration, whereas the overall US Federal budget actually increases to over $4.1 trillion.
This 2017 budget request amounts to almost $300 million less than the recently enacted NASA budget for 2016 and specifically stipulates deep funding cuts for deep space exploration programs involving both humans and robots, during President Obama’s final year in office.
The 2017 budget proposal would slash funding to the very programs designed to expand the frontiers of human knowledge and aimed at propelling humans outward to the Red Planet and robots to a Jovian moon that might be conducive to the formation of life.
Absent sufficient and reliable funding to keep NASA’s exploration endeavors on track, further launch delays are almost certainly inevitable – thereby fraying American leadership in space and science.
The administration is specifying big funding cuts to the ongoing development of NASA’s mammoth Space Launch System (SLS) heavy lift rocket and the state of the art Orion deep space crew capsule. They are the essential first ingredients to carry out NASA’s ambitious plans to send astronauts on deep space ‘Journey to Mars’ expeditions during the 2030s.
The overall Exploration Systems Development account for human deep space missions would be slashed about 18 percent from the 2016 funding level; from $4.0 Billion to only $3.3 Billion, or nearly $700 million.
SLS alone is reduced the most by $700 million from $2.0 billion to $1,31 billion, or a whopping 35 percent loss. Orion is reduced from $1.27 billion to $1.12 billion for a loss of some $150 million.
Make no mistake. These programs are already starved for funding and the Obama administration tried to force similar cuts to these programs in 2016, until Congress intervened.
Likewise, the Obama administration is proposing a draconian cut to the proposed robotic mission to Jupiter’s moon Europa that would surely delay the launch by at least another half a decade or more – to the late 2020s.
The Europa mission budget proposal is cut to only $49 million and the launch is postponed until the late 2020s. The mission received $175 million in funding in 2016 – amounting to a 72 percent reduction.
Furthermore there is no funding for a proposed lander and the launch vehicle changes from SLS to a far less powerful EELV – causing a year’s long increased travel time.
In order to maintain an SLS launch in approximately 2022, NASA would require a budget of about $150 million in 2017, said David Radzanowski, NASA’s chief financial officer, during a Feb. 9 teleconference with reporters.
Why is Europa worth exploring? Because Europa likely possesses a subsurface ocean of water and is a prime target in the search for life!
Overall, NASA’s hugely successful Planetary Sciences division suffers a huge and nearly 10 percent cut of $141 million to $1.51 billion – despite undeniably groundbreaking scientific successes this past year at Pluto, Ceres, Mars and more!
Altogether NASA would receive $19.025 billion in FY 2017. This totals $260 million less than the $19.285 billion appropriated in FY 2016, and thus corresponds to a reduction of 1.5 percent.
By contrast, the overall US Federal Budget will increase nearly 5 percent to approximately $4.1 trillion. Simple math demonstrates that NASA is clearly not a high priority for the administration. NASA’s share of the Federal budget comes in at less than half a cent on the dollar.
Orion crew module pressure vessel for NASA’s Exploration Mission-1 (EM-1) is unveiled for the first time on Feb. 3, 2016 after arrival at the agency’s Kennedy Space Center (KSC) in Florida. It is secured for processing in a test stand called the birdcage in the high bay inside the Neil Armstrong Operations and Checkout (O&C) Building at KSC. Launch to the Moon is slated in 2018 atop the SLS rocket. Credit: Ken Kremer/kenkremer.com
NASA’s Fiscal Year 2017 budget proposal was announced by NASA Administrator Charles Bolden during a televised ‘State of NASA’ address at the agency’s Langley Research Center in Virginia on Feb. 9.
Bolden did not dwell at all on the significant funding reductions for exploration.
“We are hitting our benchmarks with new exploration systems like the Space Launch System rocket and the Orion Crew Vehicle. A new consensus is emerging in the scientific and policy communities around our vision, timetable and plan for sending American astronauts to Mars in the 2030s.”
And he outlined some milestones ahead.
“We’ll continue to make great progress on the Space Launch System – SLS–rocket and we’re preparing for a second series of engine tests,” said Bolden.
“At the Kennedy Space Center, our teams will outfit Orion’s crew module with the spacecraft’s heat-shielding thermal protection systems, avionics and subsystems like electrical power storage, cabin pressure control and flight software –to name just a few.”
NASA’s Space Launch System (SLS) blasts off from launch pad 39B at the Kennedy Space Center in this artist rendering showing a view of the liftoff of the Block 1 70-metric-ton (77-ton) crew vehicle configuration. Credit: NASA/MSFC
NASA plans to launch the first combined SLS/Orion on the uncrewed Exploration Mission-1 (EM-1) in November 2018.
NASA’s Orion EM-1 crew module pressure vessel arrived at the Kennedy Space Center’s Shuttle Landing Facility tucked inside NASA’s Super Guppy aircraft on Feb 1, 2016. The Super Guppy opens its hinged nose to unload cargo. Credit: Ken Kremer/kenkremer.com
The launch date for the first crewed flight on EM-2 was targeted for 2021. But EM-2 is likely to slip to the right to 2023, due to insufficient funding.
Lack of funding will also force NASA to delay development of the far more capable and powerful Exploration Upper Stage (EUS) to propel Orion on deep space missions. It will now not be available for the SLS/EM-2 launch as hoped.
The proposed huge budget cuts to SLS, Orion and Europa are certain to arose the ire of multiple members of Congress and space interest groups, who just successfully fought to increase NASA’s FY 2016 budget for these same programs in the recently passed 2016 omnibus spending bill.
“This administration cannot continue to tout plans to send astronauts to Mars while strangling the programs that will take us there,” said Rep. Lamar Smith (R-Texas), Chairman of the House Science, Space, and Technology Committee, in a statement in response to the president’s budget proposal.
“President Obama’s FY17 budget proposal shrinks our deep space exploration programs by more than $800 million. And the administration once more proposes cuts of more than $100 million to the Planetary Science accounts, which have previously funded missions like this past year’s Pluto flyby.”
“This imbalanced proposal continues to tie our astronauts’ feet to the ground and makes a Mars mission all but impossible. This is not the proposal of an administration that is serious about maintaining America’s leadership in space.”
A “true color” image of the surface of Jupiter’s moon Europa as seen by the Galileo spacecraft. Image credit: NASA/JPL-Caltech/SETI Institute
“The Coalition for Deep Space Exploration … had hoped the request would reflect the priorities laid out for NASA in the FY16 Omnibus, for which there was broad support,” said Mary Lynne Dittmar, executive director of the Coalition for Deep Space Exploration, in a statement.
“Unfortunately this was not the case. The Coalition is disappointed with the proposed reduction in funding below the FY16 Omnibus for NASA’s exploration programs. We are deeply concerned about the Administration’s proposed cut to NASA’s human exploration development programs.”
“This proposed budget falls well short of the investment needed to support NASA’s exploration missions, and would have detrimental impacts on cornerstone, game-changing programs such as the super-heavy lift rocket, the Space Launch System (SLS), and the Orion spacecraft – the first spacecraft designed to reach multiple destinations in the human exploration of deep space.”
Homecoming view of NASA’s first Orion spacecraft after returning to NASA’s Kennedy Space Center in Florida on Dec. 19, 2014 after successful blastoff on Dec. 5, 2014. Credit: Ken Kremer – kenkremer.com
Funding for the James Webb Space Telescope (JWST) was maintained at planned levels to keep it on track for launch in 2018.
All 18 primary mirrors of NASA’s James Webb Space Telescope are seen fully installed on the backplane structure by technicians using a robotic arm (center) inside the massive clean room at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Credit: Ken Kremer/kenkremer.com
On Dec. 18, 2015, the US Congress passed and the president signed the 2016 omnibus spending bill which funds the US government through the remainder of the 2016 Fiscal Year.
As part of the omnibus bill, NASA’s approved budget amounted to nearly $19.3 Billion. That was an outstanding result and a remarkable turnaround to some long awaited good news from the decidedly negative outlook earlier in 2015.
The 2016 budget represented an increase of some $750 million above the Obama Administration’s proposed NASA budget allocation of $18.5 Billion for Fiscal Year 2016, and an increase of more than $1.2 Billion over the enacted budget for FY 2015.
And the hunt for extraterrestrial life on the icy moons of the outer solar system is postponed yet again.
Scene from ‘The Martian’ starring Matt Damon as NASA astronaut Mark Watney contemplating magnificent panoramic vista while stranded alone on Mars. Credits: 20th Century Fox
Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.
This global mosaic view of Pluto was created from the latest high-resolution images to be downlinked from NASA’s New Horizons spacecraft and released on Sept. 11, 2015. The images were taken as New Horizons flew past Pluto on July 14, 2015, from a distance of 50,000 miles (80,000 kilometers). This mosaic was stitched from over two dozen raw images captured by the LORRI imager and colorized. Right side mosaic comprises twelve highest resolution views of Tombaugh Regio heart shaped feature and shows objects as small as 0.5 miles (0.8 kilometers) in size. Credits: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/ Ken Kremer/kenkremer.com/Marco Di Lorenzo
Artist's concept of the hypothetical "Planet Nine." Could it have moons? Credit: NASA/JPL-Caltech/Robert Hurt
Artistic rendering shows the distant view from theoretical Planet Nine back towards the sun. The planet is thought to be gaseous, similar to Uranus and Neptune. Hypothetical lightning lights up the night side. Credit: Caltech/R. Hurt (IPAC)
The astronomer known worldwide for vigorously promoting the demotion of Pluto from its decades long perch as the 9th Planet, has now found theoretical evidence for a new and very distant gas giant planet lurking way beyond Pluto out to the far reaches of our solar system.
“X” marks the spot in this image transmitted to Earth on Dec. 24, 2015 from the Long Range Reconnaissance Imager (LORRI) from NASA’s New Horizons’ showing the highest-resolution swath of Pluto at the center of Sputnik Planum, the informally named plain that forms the left side of Pluto’s “heart.” The pattern of polygonal cells stems from the slow thermal convection of the nitrogen-dominated ices. Also visible is a a dirty block of water ice “floating” in denser solid nitrogen. Credits: NASA/JHUAPL/SwRI
“X” marks the spot that’s illustrative of “convective churning” resulting from subsurface planetary heating, as seen in a fascinating new super high resolution image received from NASA’s New Horizons spacecraft on Christmas Eve, Dec. 24, 2015. Its situated at the very center of the left ventricle of Pluto’s huge “heart” – an icy flow plain that’s informally named “Sputnik Planum.”
The “X” feature – see image above – is located in an area of intersecting cells, shaped like polygons, on the plains of “Sputnik Planum” which are mostly comprised of frozen nitrogen ices.
Here's an updated stamp for the newly explored Pluto. Image credit: USPS
When NASA launched New Horizons back in 2006, the spacecraft payload included your traditional of “scientific instruments” and “maneuvering thrusters”. But the engineers included a collection of nine secret items as well, including ashes from Pluto discoverer Clyde Tombaugh, and few other trinkets.
Pluto US postal stamp from 1991. Credit: JHU/APL
One noteworthy addition was a 1991 US postage stamp featuring “Pluto: Not Yet Explored”. And thus, New Horizons was carrying a symbol of its own scientific inquiry, an indication that even Pluto would get the exploration treatment when it made its closest flyby on July 13, 2015.
To celebrate this exploration, the US Postal Service has announced a new series of Pluto stamps, with updated pictures of the dwarf planet and an artist’s illustration of New Horizons.
There were a bunch of space stamps released this week, including ones celebrating Star Trek, new views of the planets, and global stamps for the Moon (send a letter anywhere on Earth, but not to the Moon, strangely). Gotta collect them all!
Planet Mercury as seen from the MESSENGER spacecraft in 2008. Credit: NASA/JPL
Virtually every planet in the Solar System has moons. Earth has The Moon, Mars has Phobos and Deimos, and Jupiter and Saturn have 67 and 62 officially named moons, respectively. Heck, even the recently-demoted dwarf planet Pluto has five confirmed moons – Charon, Nix, Hydra, Kerberos and Styx. And even asteroids like 243 Ida may have satellites orbiting them (in this case, Dactyl). But what about Mercury?
If moons are such a common feature in the Solar System, why is it that Mercury has none? Yes, if one were to ask how many satellites the planet closest to our Sun has, that would be the short answer. But answering it more thoroughly requires that we examine the process through which other planets acquired their moons, and seeing how these apply (or fail to apply) to Mercury.
