A brand new crater on the Moon! This new 12 meter (39 foot) diameter impact crater formed between 25 October 2012 and 21 April 2013 Credit: NASA/GSFC/Arizona State University].
Animation of a temporal pair of the new 39-foot (12-meter) impact crater on the moon photographed by NASA’s Lunar Reconnaissance Orbiter Credit: NASA/GSFC/Arizona State University
We often hear how the Moon’s appearance hasn’t changed in millions or even billions of years. While micrometeorites, cosmic rays and the solar wind slowly grind down lunar rocks, the Moon lacks erosional processes such as water, wind and lurching tectonic plates that can get the job done in a hurry.
One of a series of photos Apollo 11 astronaut Edwin Aldrin made of his bootprint in the dusty, sandy lunar soil, called regolith. Based on a newy study, the impression may disappear in a few tens of thousands of years instead a few million. Credit: NASA
Remember Buzz Aldrin’s photo of his boot print in the lunar regolith? It was thought the impression would last up to 2 million years. Now it seems that estimate may have to be revised based on photos taken by the Lunar Reconnaissance Orbiter (LRO) that reveal that impacts are transforming the surface much faster than previously thought.
This map shows the distribution of new impact craters (yellow dots) discovered by analyzing 14,000 narrow-angle camera (NAC) temporal pairs. The two red dots mark the location of the March 17, 2013 and September 11, 2013 impacts that were recorded by Earth-based video monitoring. LRO’s mission was recently extended an addition two years through September 2018. Credit: NASA/GSFC/ASUThe LRO’s high resolution camera, which can resolve features down to about 3 feet (1-meter) across, has been peering down at the Moon from orbit since 2009. Taking before and after images, called temporal pairs, scientists have identified 222 impact craters that formed over the past 7 years. The new craters range from 10 feet up to 141 feet (3-43 meters) in diameter.
By analyzing the number of new craters and their size, and the time between each temporal pair, a team of scientists from Arizona State University and Cornell estimated the current cratering rate on the Moon. The result, published in Nature this week, was unexpected: 33% more new craters with diameters of at least 30 feet (10 meters) were found than anticipated by previous cratering models.
LRO before and after images of an impact event on March 17, 2013. The newly formed crater is 59 feet (18 meters) in diameter. Subsurface regolith not exposed to sunlight forms a bright halo around the new crater. There also appears to be a larger nimbus of darker reflectance material visible much further beyond but centered on the impact. Credit: NASA/GSFC/Arizona State University
Similar to the crater that appeared on March 17, 2013 (above), the team also found that new impacts are surrounded by light and dark reflectance patterns related to material ejected during crater formation. Many of the larger impact craters show up to four distinct bright or dark reflectance zones. Nearest to the impact site, there are usually zone of both high and low reflectance. These two zones likely formed as a layer of material that was ejected from the crater during the impact shot outward to about 2½ crater diameters from the rim.
An artist’s illustration of a meteoroid impact on the Moon. Impacts dig up fresh material from below as well as send waves of hot rock vapor and molten rock across the lunar landscape, causing a much faster turnover of the moon soil than previously thought. Credit: NASA
From analyzing multiple impact sites, far flung ejecta patterns wrap around small obstacles like hills and crater rims, indicating the material was traveling nearly parallel to the ground. This kind of path is only possible if the material was ejected at very high speed around 10 miles per second or 36,000 miles per hour! The jet contains vaporized and molten rock that disturb the upper layer of lunar regolith, modifying its reflectance properties.
How LRO creates temporal pairs and scientists use them to discover changes on the moon’s surface.
In addition to discovering impact craters and their fascinating ejecta patterns, the scientists also observed a large number of small surface changes they call ‘splotches’ most likely caused by small, secondary impacts. Dense clusters of these splotches are found around new impact sites suggesting they may be secondary surface changes caused by material thrown out from a nearby primary impact. From 14,000 temporal pairs, the group identified over 47,000 splotches so far.
Here are two examples of a low reflectance (top) and high reflectance (bottom) splotch created either by a small impactor or more likely from secondary ejecta. In either case, the top few inches of the regolith (soil) was churned Credit: NASA/GSFC/Arizona State UniversityBased on estimates of size, depth and frequency of formation, the group estimated that the relentless churning caused by meteoroid impacts will turn over 99% of the lunar surface after about 81,000 years. Keep in mind, we’re talking about the upper regolith, not whole craters and mountain ranges. That’s more than 100 times faster than previous models that only took micrometeorites into account. Instead of millions of years for those astronaut boot prints and rover tracks to disappear, it now appears that they’ll be wiped clean in just tens of thousands!
The Full Moon of August 18, 2016 rises amid cloud over a wheat field. Friday night will see the rising of the annual Harvest Moon. Credit: Alan Dyer
It’s that wonderful time of year again when the Harvest Moon teeters on the horizon at sunset. You can watch the big orange globe rise on Friday (Sept. 16) from your home or favorite open vista just as soon as the Sun goes down. Despite being one of the most common sky events, a Full Moon rise still touches our hearts and minds every time. No matter how long I live, there will never be enough of them.
Friday night’s Harvest Moon rises around sunset in the faint constellation Pisces the fish. Watch for it to come up almost due east around the time of sunset. Once the sky gets dark, look two fists above and left of the Moon for the four stars that outline the spacious asterism of Pegasus the flying horse. Stellarium
To see a moonrise, the most important information you need is the time the moon pops up for your city, which you’ll find by using this Moonrise and Moonset calculator. Once you know when our neighborly night light rises, pre-arrange a spot you can walk or drive to 10-15 minutes beforehand. The waiting is fun. Who will see it first? I’ll often expect to see the Moon at a certain point along the horizon then be surprised it’s over there.
A photographer finds just the right spot in Duluth along Lake Superior to photograph a rising Full Moon. The flattened shape of the Moon is caused by the layer of denser air closer to the horizon refracting or bending the bottom half of the Moon more strongly than the thinner air along the top limb. In effect, refraction “lifts” the bottom half of the Moon upward into the top to give it a squashed appearance. Once the Moon rises high enough so we see it through much thinner (less dense) air, refraction becomes negligible and the Moon assumes its more familiar circular shape. Credit: Bob King
Depending on how low to the horizon you can see, it’s possible, especially over water, to catch the first glimpse of lunar limb breaching the horizon. This still can be a tricky feat because the Moon is pale, and when it rises, shows little contrast against the still-bright sky. Since the Moon moves about one outstretched fist to the east (left in the northern hemisphere) each night, if you wait until one night after full phase, the Moon will rise in a much darker sky and appear in more dramatic contrast against the sky background.
This photo sequence showing an extraordinary moonset taken from the shores of Garrison Lake in Port Orford, Oregon. “The distortion that occurred as it descended was quite remarkable — the Moon’s shape was changing as fast as I could snap a picture,” said photographer Randy Scholten. As the Moon rises, we peer through hundreds of miles of the lower atmosphere, where the air is densest and dustiest. Aerosols scatter much of the blues and greens in moonlight away, leaving orange and red. Turbulence and varying air densities along the line of sight can create all manner of distortions of the lunar disk. Credit: Randy Scholten
Look closely at the rising Moon with both naked eye and binoculars and you might just see a bit of atmospheric sorcery at work. Refraction, illustrated the icy moonrise image above, is the big one. It creates the squashed Moon shape. But more subtle things are happening that depend on how turbulent or calm the air is along your line of sight to our satellite.
Clouds add their own beauty and mystery to the rising Moon. Credit: Bob King
Rippling waves “sizzling” around the lunar circumference can be striking in binoculars though the effect is quite subtle with the naked eye. Much easier to see without any optical aid are the weird shapes the Moon can assume depending upon the state of the atmosphere. It can looked stretched out like a hot air balloon, choppy with a step-like outline around its bottom or top, square, split into two moons or even resemble a “mushroom cloud”.
If you make a point to watch moonrises regularly, you’ll become acquainted as much with Earth’s atmosphere as with the alien beauty of our sole satellite.
This Full Moon is special in at least two ways. First, it will undergo a penumbral eclipse for skywatchers across eastern Europe, Africa, Asia and Australia. Observers there should watch a dusky gray shading over the upper or northern half of the Moon around the time of maximum eclipse. The link will take you to Dave Dickinson’s excellent article that appeared earlier here at Universe Today.
The angle of the moon’s path to the horizon makes all the difference in moonrise times. At full phase in spring, the path tilts steeply southward, delaying successive moonrises by over an hour. In September, the moon’s path is nearly parallel to the horizon with successive moonrises just 20+ minutes apart. Times shown are for illustration only — so you can see the dramatic different in rise times — and don’t refer necessarily to Friday night’s moonrise. Illustration: Bob King
In the northern hemisphere, September’s Full Moon is named the Harvest Moon, defined as the Full Moon closest to the autumnal equinox, which occurs at 9:21 a.m. CDT (14:21 UT) on the 22nd. Normally, the Moon rises on average about 50 minutes later each night as it moves eastward along its orbit. But at Harvest Moon, successive moonrises are separated by a half-hour or less as viewed from mid-northern latitudes. The short gap of time between between bright risings gave farmers in the days before electricity extra light to harvest their crops, hence the name.
Use your imagination and you can see any of several figures in the Full Moon composed of contrasting maria and highlands.
Why the faster-than-usual moonrises? Every September, the Full Moon’s nightly travels occur at a shallow angle to the horizon; as the moon scoots eastward, it’s also moving northward this time of year as shown in the illustration above. The northern and eastward motions combine to make the Moon’s path nearly level to the horizon. For several nights in a row, it only takes a half-hour for the Earth’s rotation to carry the Moon up from below the horizon. In spring, the angle is steep because the Moon is then moving quickly southward along or near the ecliptic, the path it takes around the sky. Rising times can exceed an hour.
As you gaze at the Moon over the next several nights, take in the contrast between its ancient crust, called the lunar highlands, and the darker seas (also known as maria, pronounced MAH-ree-uh). The crust appears white because it’s rich in calcium and aluminum, while the maria are slightly more recent basaltic lava flows rich in iron, which lends them a darker tone. Thanks to these two different types of terrain it’s easy to picture a male or female face or rabbit or anything your imagination desires.
The massive Saturn V rocket launches the Apollo 11 mission to the Moon on July 16, 1969. Image: NASA
A bag that travelled to the Moon and back is at the heart of a legal dispute involving NASA and a woman named Nancy Carlson. Carlson currently owns the bag and obtained it legally. But NASA is in possession of the bag, and the US Attorney’s Office wants the courts to quash Carlson’s purchase of the bag, so they can retain ownership of this important piece of space memorabilia.
The lawsuit over the lunar sample bags was first reported by Roxana Hegeman of the Associated Press, and covered by Robert Pearlman at collectspace.com.
The story of the Apollo 11 bag is bit of a tangled web. To understand it, we have to look at a third figure, Max Ary. Ary was the founder and long-time director of the Kansas Cosmosphere and Space Center. In 2005, Ary was convicted for stealing and selling museum artifacts.
Hundreds of space artifacts and memorabilia, some on loan from NASA, had gone missing. In 2003, the Apollo 11 bag was found in a box in Ary’s garage during the execution of a search warrant as part of the case against him. However, the bag was misidentified due to a spreadsheet error, and sold to Carlson at a government auction for $995.
Sample collection on the surface of the Moon. Apollo 16 astronaut Charles M. Duke Jr. is shown collecting samples with the Lunar Roving Vehicle in the left background. Image: NASA
NASA only found out about the Apollo 11 bag after Carlson purchased it. Carlson sent it to the Johnson Space Center in Houston to be authenticated. Once NASA realized what the bag was, they set the legal process in motion to set aside the forfeiture and sale. The US Attorney’s office argued that NASA was not properly notified of the bag’s forfeiture because it was not labelled properly.
NASA’s attorney’s wrote “NASA was denied the opportunity to assert its interest in the lunar bag. Had NASA been given notice of the forfeiture action and/or had all the facts about the lunar bag been known, the lunar [sample return] bag would never have gone to a government auction.”
The attorneys added that “The true identity and ownership of the lunar bag are now known. The failure to give proper notice to NASA can be corrected by setting aside the forfeiture and rescinding its sale,” they stated. “These are unusual circumstances that warrant the particular relief sought.”
If this seems like quite a bit of fuss over a bag, remember that this bag travelled to the Moon and back, making it very rare. Apollo 11 astronauts used it to collect the first samples from the Moon, and dust fragments from the Moon are embedded in its fabric. It’s a very valuable historic and scientific artifact. The government said in a statement that the bag is “a rare artifact, if not a national treasure.”
Carlson, who obtained the bag legally at an auction, is an attorney and is now suing NASA for “unwarranted seizure of my personal property… without any legal provocation.” This after she voluntarily submitted the bag to NASA for authentication, and after NASA offered to reimburse her purchase price and an additional $1,000 dollars “in appreciation for your assistance in returning the bag” and “to offset any inconvenience you may have suffered.”
There’s no question that artifacts like these belong in NASA’s public collection, and on display in a museum. But Carlson obtained the bag through a legal auction. Maybe, as the bag’s purchaser, Carlson is hoping that NASA will tender a larger offer for return of the bag, and she can make some profit. That’s pure speculation of course. Perhaps she’s just very keen on owning this piece of history.
As for Max Ary, the man who set all this in motion years ago, he is now out of prison and maintains his innocence. Ary collected other space artifacts and memorabilia and sold them from his home, and he claims that it was just a mix up. He was convicted though, and he served just over 2 years of his 3 year prison sentence. He was also ordered to pay $132,000 in restitution.
This map shows the 23% illuminated crescent Moon from the central U.S. around 10:00 UT Friday morning. Observers who start observing earlier may also see stars in the Hyades cluster occulted. Credit: Stellarium
We’re in for a celestial show from two of the sky’s glitterati this week. On Friday morning July 29 around 10:00 UT (5 a.m. CDT), the crescent Moon will occult the star Aldebaran from the eastern and southern U.S. south of a line from Toledo, Ohio through St. Louis, Tulsa and El Paso, Texas. North of that line, the Moon will slide just south of the star in a spectacular conjunction. But the real action lies within a half-mile of either side of the line, where lucky observers will see a grazing occultation.
Use this map to help you plan your occultation adventure. Much of North and South America will see a wonderful conjunction, while many areas will witness the occultation. If you can drive to the graze line, do it! Credit: David Dunham
As the Moon’s orbital motion carries it eastward at the rate of one lunar diameter per hour, Aldebaran will appear to approach the sunlit northern cusp and then scrape along the Moon’s northern limb. You’ll need binoculars or a small telescope to see the initial approach, but once star reaches the semi-dark, earthlit portion of the Moon, the graze will be visible with the naked eye.
This diagram shows the the grazing path of Aldebaran. As the Moon moves east, the star will appear to move to the right or west. Be sure not to miss it — the entire grazing event lasts just 3 minutes. Credit: David Dunham
The edge or limb of the Moon appears smooth to the eye, but it’s rife with polar mountain peaks. As Aldebaran creeps along the craggy limb, it will repeatedly flash in and out of view as peaks and cliffs momentarily block it from sight. And here’s the truly amazing thing. Observers along the western section of the graze line, where the event takes place in fairly dark sky, can watch the star blink in and out of view without optical aid when it reaches the dark part of the lunar disk. Wow!
Aldebaran’s large size means it won’t disappear instantaneously when it’s covered either by the lunar limb during occultation or by mountains along the grazing path. Credit: Wikipedia
Aldebaran is no small star. An orange giant 67 light years from Earth, it’s 44 times the diameter of the Sun. That means that sometimes only a part of the star at a time will covered at a time in some cases, so the length of the flashes will vary. According to David Dunham, president of the International Occultation Timing Association (IOTA), Aldebaran will disappear for one-tenth of a second up to a second as the Moon rolls east, allowing some observers to sense the size of the star. Wow x 100!
Aldebaran hangs near the edge of the moon two minutes before it was occulted last October in this photo taken with a smartphone. The star was easily visible through the telescope. Credit: Bob King
Skywatchers further east along the graze line and in other areas where the occultation / conjunction takes place after sunrise shouldn’t pass up the chance to see the event. During last October’s occultation of Aldebaran, I was able to see and photograph the star in my 10-inch scope in daylight no problem. The moon will be closer to the Sun this time around, but give it try anyway. This is the best grazing occultation of Aldebaran visible from North America in the current 4-year series.
For the many who live either north or south of the graze line, the views will still be fantastic. You’ll either see an occultation and subsequent reappearance of the star at the dark limb … or a fine conjunction. The forecast looks good for my city, so I plan on heading out to watch an orange giant meet the skinny Moon. I wish you clear skies and happy shooting!
For more information about the event including detailed weather forecasts and grazing maps, check out the IOTA’s public announcement page. Click here for Universal Times for the disappearance and reappearance of the star for over 1,000 cities.
Mercury and the Moon over the ramparts of Assilah, Morocco. Photo by author
Have you caught sight of Mercury yet? This coming week is a good time to try, looking low to the west at dusk. We just managed to to nab it with binoculars for the first time during the current apparition this past Sunday from the rooftop of our Air BnB in Casablanca, Morocco.
Mercury is a tough grab under any circumstance, that’s for sure. Brilliant Venus and Jupiter make great guides to finding the elusive planet in late July, as it ping-pongs between the two. The waxing crescent Moon joins the scene in the first week of August, and for a very lucky few, actually occults (passes in front of ) the diminutive innermost world shortly after passing New.
Mercury (arrowed) near the Moon on the morning of June 3rd, 2016. Image credit: Dave Dickinson.
Here’s the low down on everything Mercurial, and circumstances for the coming weeks.
Mercury passes 18′ from the star Regulus on Saturday, July 30th at 19:00 Universal Time (UT), representing the closest passage of a planet near a first magnitude star for 2016.
The Moon then reaches New phase, marking the start of lunation 1158 on August 2nd at 20:45 UT. The Moon then moves on to occult Mercury on Thursday, August 4th at 22:00 UT, just over 48 hours later. The occultation is visible at dusk for observers based in southern Chile and southern Argentina. The rest of us see a close pass. Note that although it is a miss for North America, viewers based on the continent share the same colongitude and will see Mercury only a degree off of the northern limb of the Moon on the night of August 4th. Mercury shines at magnitude +0.01, and presents a 67% illuminated disk 6.3” in size, while the Moon is a slender 5% illuminated.
Occultations of Mercury for 2016. Credit: Occult 4.2. (click image to enlarge).
How early can you see the waxing crescent Moon? Catching the Moon with the naked eye under transparent clear skies isn’t usually difficult when it passes 20 hours old. This cycle, first sightings favor South Africa westward on the night of August 3rd.
Mercury reaches greatest elongation 27.4 degrees east of the Sun 12 days after this occultation on August 16th.
How rare is it? Well occultations of Mercury by the Moon are the toughest to catch of all the naked eye planets, owing to the fact that the planet never strays far from the Sun. Nearly all of these events go unwitnessed, as they occur mainly under daytime skies. And while you can observe Mercury in the daytime near greatest elongation with a telescope, safety precautions need to be taken to assure the Sun is physically blocked from view. Astronomers of yore did exactly that, hoping to glimpse fleeting detail on Mercury while it was perched higher in the sky above the murk of the atmosphere low to the horizon.
In fact, a quick search of ye ole web reveals very few convincing captures of an occultation of Mercury (see the video above). The closest grab thus far comes from astrophotographer Cory Schmitz on June 3rd 2016 based in South Africa:
Can you see it? The Moon about to occult Mercury on June 3rd. Image credit and copyright: Cory Schmitz.
Can’t wait til next week? The Moon crosses the Hyades open star cluster this week, occulting several stars along the way. The action occurs on the morning of Friday, July 29th culminating with an occultation of +1 magnitude Aldebaran by the 23% illuminated Moon. Texas and Mexico are well-placed to see this event under dark skies. A small confession: we actually prefer occultations of planets and stars by the waxing Moon, as the dark edge of the Moon is leading during ingress, making it much easier to witness and the exact moment the Moon blots out the object.
Still want more? The Moon actually goes on to occult Jupiter on August 6th for the South Pacific. Viewers farther west in southeast Asia might just spy this one in the daytime. This is the second occultation of Jupiter by the Moon in a series of four in 2016.
Looking west on the evening of August 4th. Image credit: Stellarium.
Keep and eye on those planets in August, as they’re now all currently visible in the dusk sky. The Moon, Regulus and Venus also form a tight five degree triangle on the evening of August 4th, followed by a slightly wider grouping of Venus, Jupiter and the Moon around August 25th.
More to come on that soon. Be sure to check the planet Mercury off of your life list this coming week, using the nearby waxing crescent Moon as a guide.
A photo of the full moon, taken from Apollo 11 on its way home to Earth, from about 18,520 km (10,000 nm) away. Credit: NASA
The asteroid that punched an “eye” in the Moon is about 10 times more massive than originally thought. Researchers say a protoplanet-sized body slammed into the Moon about 3.8 billion years ago, creating the area called Imbrium Basin that forms the right eye of the so-called “Man in the Moon.” Additionally, this large body also indicates that protoplanet-sized asteroids may have been common in the early solar system, putting the “heavy” into the Late Heavy Bombardment.
“We show that Imbrium was likely formed by an absolutely enormous object, large enough to be classified as a protoplanet,” said Pete Schultz from Brown University. “This is the first estimate for the Imbrium impactor’s size that is based largely on the geological features we see on the Moon.”
Mare Imbrium or the Sea of Showers is highlighted in this map of the moon. The other large, dark spots are also basins created from asteroid impacts. Credit: NASA
The Imbrium Basin is easily seen when the Moon is full, as a dark patch in the Moon’s northwestern quadrant. It is about 750 miles across, and a closer look shows the basin is surrounded by grooves and gashes that radiate out from the center of the basin, plus a second set of grooves with a different alignment that have puzzled astronomers for decades.
To re-enact the impact, Schultz used the Vertical Gun Range at the NASA Ames Research Center to conduct hypervelocity impact experiments. This facility has a 14-foot cannon that fires small projectiles at up to 25,750 km/hr (16,000 miles per hour), and high-speed cameras record the ballistic dynamics. During his experiments, Schultz noticed that in addition to the usual crater ejecta from the impact, the impactors themselves – if large enough — had a tendency to break apart when they first made contact with the surface. Then these chunks would continue to travel at a high speeds, skimming along and plowing across the surface, creating grooves and gouges.
Grooves and gashes associated with the Imbrium Basin on the Moon have long been puzzling. New research shows how some of these features were formed and uses them to estimate the size of the Imbrium impactor. The study suggests it was big enough to be considered a protoplanet. NASA/Northeast Planetary Data Center/Brown University
The results showed the second set of grooves were likely formed by these large chunks of the impactor that sheared off on initial contact with the surface.
“The key point is that the grooves made by these chunks aren’t radial to the crater,” Schultz said in a press release. “They come from the region of first contact. We see the same thing in our experiments that we see on the Moon — grooves pointing up-range, rather than the crater.”
The second set of groove trajectories could be used to estimate the impactor’s size. Schultz worked with David Crawford of the Sandia National Laboratories to generate computer models of the physics of various sizes of impactors, and they were able to estimate the impactor that created Imbrium Basin to be more than 250 km (150 miles) across, which is two times larger in diameter and 10 times more massive than previous estimates. This puts the impactor in the range of being the size of a protoplanet.
“That’s actually a low-end estimate,” Schultz said. “It’s possible that it could have been as large as 300 kilometers.”
Previous estimates, Schultz said, were based solely on computer models and yielded a size estimate of only about 50 miles in diameter.
Schultz and his colleagues also used the same methods to estimate the sizes of impactors related to several other basins on the Moon, for example, the Moscoviense and Orientale basins on the Moon’s far side, which yielded impactor sizes of 100 and 110 kilometers across respectively, larger than some previous estimates.
Combining these new estimates with the fact that there are even larger impact basins on the Moon and other planets, Schultz concluded that protoplanet-sized asteroids may have been common in the early solar system, and he called them the “lost giants” of the Late Heavy Bombardment, a period of intense comet and asteroid bombardment thought to have pummeled the Moon and all the planets including the Earth about 4 to 3.8 billion years ago.
“The Moon still holds clues that can affect our interpretation of the entire solar system,” he said. “Its scarred face can tell us quite a lot about what was happening in our neighborhood 3.8 billion years ago.”
NASA's Deep Space Climate Observatory captured a series of images of the Moon passing in front of the Earth on July 5th. Image: NASA/NOAA
We’re accustomed to seeing stunning images of both the Moon and Earth floating in space. It’s the age we live in. But seeing them together is rare. Now, NASA’s Deep Space Climate Observatory (DSCOVR) has captured images of the Moon passing between itself and the Earth, in effect photo-bombing Earth.
The image was captured with the Earth Polychromatic Imaging Camera (EPIC) camera on DISCOVR, and is the second time this has been captured. EPIC is a 4 megapixel camera on board DSCOVR, and DSCOVR is in orbit about 1.6 million km (1 million miles) from Earth, between the Earth and the Sun.
“For the second time in the life of DSCOVR, the moon moved between the spacecraft and Earth,” said Adam Szabo, DSCOVR project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
Cool pictures of the Moon are a bonus, though, as DSCOVR’s primary mission is to monitor the solar wind in real time for the National Oceanic and Atmospheric Administration (NOAA). It does so while inhabiting the first LaGrange point between the Earth and the Sun, where the gravitational pull of the Sun and the Earth balance each other. To do so requires a complex orbit called a Lissajous orbit, a non-recurring orbit which takes DSCOVR from an ellipse to a circle and back.
DSCOVR occupies the LaGrange point 1 between the Earth and the Sun. Image: NOAA
DSCOVR has other important work to do. From its vantage point, DSCOVR keeps a constantly illuminated view of the surface of the Earth as it rotates. DSCOVR provides observations of cloud height, vegetation, ozone, and aerosols in the atmosphere. This is important scientific data in monitoring and understanding Earth’s climate.
DSCOVR is a partnership between NASA, NOAA and the U.S. Air Force. As mentioned above, its primary objective is maintaining the nation’s real-time solar wind monitoring capabilities, which are critical to the accuracy and lead time of space weather alerts and forecasts from NOAA. The DSCOVR website also has daily color pictures of the Earth, for all your eye-candy needs.
We’ve had an abundance of news stories for the past few months, and not enough time to get to them all. So we are now using a tool called Trello to submit and vote on stories we would like to see covered each week, and then Fraser will be selecting the stories from there. Here is the link to the Trello WSH page (http://bit.ly/WSHVote), which you can see without logging in. If you’d like to vote, just create a login and help us decide what to cover!
We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Google+, Universe Today, or the Universe Today YouTube page.
Earth has a new quasi-moon: an asteroid called 2016 H03. (Not shown) Image: NASA
Earth has a small companion that NASA is calling an almost-Moon. The small asteroid, called 2016 H03, isn’t quite a moon because it’s actually orbiting the Sun. In its orbit around the Sun, it spends about half of its time closer to the Sun than the Earth.
2016 H03 is called a “quasi-moon” or a “near-Earth companion”. It doesn’t quite qualify as a moon because of its orbit.
Paul Chodas is the manager of NASA’s Center for Near-Earth Object (NEO) Studies at the Jet Propulsion Laboratory in Pasadena, California. He had this to say about 2016 H03: “Since 2016 HO3 loops around our planet, but never ventures very far away as we both go around the sun, we refer to it as a quasi-satellite of Earth.”
2016 H03’s orbit is tilted relative to Earth’s, and it passes through the plane of Earth’s orbit. Over the decades, it also performs a slow, back and forth twist. NASA describes 2016 H03’s orbit as a game of leap frog.
“The asteroid’s loops around Earth drift a little ahead or behind from year to year, but when they drift too far forward or backward, Earth’s gravity is just strong enough to reverse the drift and hold onto the asteroid so that it never wanders farther away than about 100 times the distance of the moon,” said Chodas. “The same effect also prevents the asteroid from approaching much closer than about 38 times the distance of the moon. In effect, this small asteroid is caught in a little dance with Earth.”
Earth’s little quasi-moon has been in its stable orbit for about a century, according to calculations, though it was only spotted on April 27th, 2016, by the Pan-STARRS 1 asteroid survey telescope in Hawaii. Pan-STARRS 1 is operated by the University of Hawaii’s Institute for Astronomy and NASA’s Planetary Defense Coordination Office. (Did you know we had a Planetary Defense Coordination Office?)
2016 H03 is small. It’s exact size has not been established, but it’s between 40 and 100 meters (120 and 300 ft.) It’s been around a century, and calculations say it will be around for centuries more.
2016 H03 is not quite unique. Earth has had other dance partners like it.
“One other asteroid — 2003 YN107 — followed a similar orbital pattern for a while over 10 years ago, but it has since departed our vicinity. This new asteroid is much more locked onto us. Our calculations indicate 2016 HO3 has been a stable quasi-satellite of Earth for almost a century, and it will continue to follow this pattern as Earth’s companion for centuries to come,” said Chudas.
NASA tracks thousands of NEOs and assesses their risk of collision with Earth. Though 2016 H03 is an interesting specimen because of its orbit, it poses no threat to Earth.
New research finds that asteroids delivered as much 80 percent of the Moon's water. Credit: LPI/David A. Kring
Over the course of the past few decades, our ongoing exploration the Solar System has revealed some surprising discoveries. For example, while we have yet to find life beyond our planet, we have discovered that the elements necessary for life (i.e organic molecules, volatile elements, and water) are a lot more plentiful than previously thought. In the 1960’s, it was theorized that water ice could exist on the Moon; and by the next decade, sample return missions and probes were confirming this.
Since that time, a great deal more water has been discovered, which has led to a debate within the scientific community as to where it all came from. Was it the result of in-situ production, or was it delivered to the surface by water-bearing comets, asteroids and meteorites? According to a recent study produced by a team of scientists from the UK, US and France, the majority of the Moon’s water appears to have come from meteorites that delivered water to Earth and the Moon billions of years ago.
For the sake of their study, which appeared recently in Nature Communications, the international research team examined the samples of lunar rock and soil that were returned by the Apollo missions. When these samples were originally examined upon their return to Earth, it was assumed that the trace of amounts of water they contained were the result of contamination from Earth’s atmosphere since the containers in which the Moon rocks were brought home weren’t airtight. The Moon, it was widely believed, was bone dry.
The blue areas show locations on the Moon’s south pole where water ice is likely to exist. Credit: NASA/GSFC
However, a 2008 study revealed that the samples of volcanic glass beads contained water molecules (46 parts per million), as well as various volatile elements (chlorine, fluoride and sulfur) that could not have been the result of contamination. This was followed up by the deployment of the Lunar Reconnaissance Orbiter (LRO) and the Lunar Crater Observation and Sensing Satellite (LCROSS) in 2009, which discovered abundant supplies of water around the southern polar region,
However, that which was discovered on the surface paled in comparison the water that was discovered beneath it. Evidence of water in the interior was first revealed by the ISRO’s Chandrayaan-1 lunar orbiter – which carried the NASA’s Moon Mineralogy Mapper (M3) and delivered it to the surface. Analysis of this and other data has showed that water in the Moon’s interior is up to a million times more abundant than what’s on the surface.
The presence of so much water beneath the surface has begged the question, where did it all come from? Whereas water that exists on the Moon’s surface in lunar regolith appears to be the result of interaction with solar wind, this cannot account for the abundant sources deep underground. A previous study suggested that it came from Earth, as the leading theory for the Moon’s formation is that a large Mars-sized body impacted our nascent planet about 4.5 billion years ago, and the resulting debris formed the Moon. The similarity between water isotopes on both bodies seems to support that theory.
Near-infrared image of the Moon’s surface by NASA’s Moon Mineralogy Mapper on the Indian Space Research Organization’s Chandrayaan-1 mission. Credit: ISRO/NASA/JPL-Caltech/Brown Univ./USGS
However, according to Dr. David A. Kring, a member of the research team that was led by Jessica Barnes from Open University, this explanation can only account for about a quarter of the water inside the moon. This, apparently, is due to the fact that most of the water would not have survived the processes involved in the formation of the Moon, and keep the same ratio of hydrogen isotopes.
Instead, Kring and his colleagues examined the possibility that water-bearing meteorites delivered water to both (hence the similar isotopes) after the Moon had formed. As Dr. Kring told Universe Today via email:
“The current study utilized analyses of lunar samples that had been collected by the Apollo astronauts, because those samples provide the best measure of the water inside the Moon. We compared those analyses with analyses of meteoritic samples from asteroids and spacecraft analyses of comets.”
By comparing the ratios of hydrogen to deuterium (aka. “heavy hydrogen”) from the Apollo samples and known comets, they determined that a combination of primitive meteorites (carbonaceous chondrite-type) were responsible for the majority of water to be found in the Moon’s interior today. In addition, they concluded that these types of comets played an important role when it comes to the origins of water in the inner Solar System.
Images produced by the Lyman Alpha Mapping Project (LAMP) aboard NASA’s Lunar Reconnaissance Orbiter reveal features at the Moon’s northern and southern poles, as well as the presence of water frost. Credit: NASA/SwRI
For some time, scientists have argued that the abundance of water on Earth may be due in part to impacts from comets, trans-Neptunian objects or water-rich meteoroids. Here too, this was based on the fact that the ratio of the hydrogen isotopes (deuterium and protium) in asteroids like 67P/Churyumov-Gerasimenko revealed a similar percentage of impurities to carbon-rich chondrites that were found in the Earth’s coeans.
But how much of Earth’s water was delivered, how much was produced indigenously, and whether or not the Moon was formed with its water already there, have remained the subject of much scholarly debate. Thank to this latest study, we may now have a better idea of how and when meteorites delivered water to both bodies, thus giving us a better understanding of the origins of water in the inner Solar System.
“Some meteoritic samples of asteroids contain up to 20% water,” said Kring. “That reservoir of material – that is asteroids – are closer to the Earth-Moon system and, logically, have always been a good candidate source for the water in the Earth-Moon system. The current study shows that to be true. That water was apparently delivered 4.5 to 4.3 billion years ago.“
The existence of water on the Moon has always been a source of excitement, particularly to those who hope to see a lunar base established there someday. By knowing the source of that water, we can also come to know more about the history of the Solar System and how it came to be. It will also come in handy when it comes time to search for other sources of water, which will always be a factor when trying to establishing outposts and even colonies throughout the Solar System.
![Distribution of new impact craters (yellow dots) discovered by analyzing 14,000 NAC temporal pairs. The two red dots mark the location of the 17 March 2013 and the 11 September 2013 impacts that were recorded by Earth-based video monitoring [NASA/GSFC/Arizona State University]](https://www.universetoday.com/wp-content/uploads/2016/10/Moon-new-crater-distribution-NASA-GSFC-ASU.jpg)
![Example of a low reflectance (top) and high reflectance (bottom) splotch created either by a small impactor or more likely from secondary ejecta. In either case, the top few centimeters of the regolith (soil) was churned [NASA/GSFC/Arizona State University].](https://www.universetoday.com/wp-content/uploads/2016/10/Moon-craters-splotches-NASA.gif)
