Visions of Earth through the Yutu Rover’s Eyes

Last night I used my telescope to eye-hike the volcanic plains of the Sea of Rains (Mare Imbrium) where the Yutu rover and lander sit beneath a blistering sun. With no atmosphere to speak of and days that last two weeks, noontime temperatures can hit 250 degrees Fahrenheit (122 C) . That’s hot enough that mission control at the Beijing Aerospace Command and Control Center has decided to draw the shades and give the rover a nap from science duties until December 23 when things cool down a bit.

While studying the subtle gray hues of the Imbrium lava flows I got to wondering what the sky might look like if I could don a spacesuit and visit the landing site “where the skies are not cloudy all day” (to quote a famous song). With no atmosphere to speak of, stargazing can be done both day and night on the moon though I suspect it’s better at night when there’s less glare from your surroundings. Night, defined as the time from sunset to sunrise (no twilights here), lasts about 14.5 Earth days. Days are equally long.

Lunar landscape photographed by the Chang'e 3 lander on Dec. 15, 2013. Credit: CCTV
Lunar landscape photographed by the Chang’e 3 lander on Dec. 15, 2013. Credit: CCTV

 

From Yutu’s point of view, it’s very nearly lunar noon today (Dec. 19) with the sun halfway up in the southern sky.  Looking at the map of the sky from the lander’s location, you’ll see a few familiar constellations and one very familiar planet – Earth!

Phases of the moon and Earth are complementary. When the moon is full, Earth's a crescent. This map shows the Earth in Capricornus on Dec. 20 as thin blue crescent. Stellarium
Phases of the moon and Earth are complementary. When the moon is full, Earth’s a crescent. This map shows the Earth in Capricornus on Dec. 20 as thin blue crescent. Stellarium

Today Earth appears as a very thin crescent a short distance to the left or east of the sun. Because the moon takes just as long to rotate on its axis as it does to revolve around the Earth, the same face of the moon always faces our planet. Because the two are in synchrony, astronomers call it synchronous rotation.

From the perspective of someone standing on the moon, Earth stands still in one spot of sky throughout the 29.5 day lunar day-night cycle. Well, not perfectly still. Because the moon’s orbit is inclined about 5 degrees to Earth’s orbit and its speed varies along its non-circular orbit, Earth describes a little circle in the lunar sky about 10 degrees in diameter every four weeks.

As the sun slowly moves off to the west, our blue planet remains nearly stationary from Yutu’s perspective and undergoes all the familiar phases we see the moon experience back here on Earth: an evening crescent to start followed by a first quarter Earth, Full Earth last quarter and finally, New Earth. I like the ring of that last one.

The lunar landscape at the rover's location is bathed in pale blue light on Dec. 31, 2013 during "Full Earth". Stellarium
The lunar landscape at the rover’s location is bathed in pale blue light on Dec. 31, 2013 during a Full Earth. Stellarium

Yutu and the lander will see the sun drift to the west while Earth moves east, rises higher in the lunar sky and putting on the pounds phase-wise. Today Earth’s glides across the border of Sagittarius into Capricornus. The next Full Earth happens on New Year’s Eve when the sun is directly opposite the Earth in the lunar sky.

Full Earth always happens around local midnight or about one week before sunrise during the long lunar day. On the moon the sun is up for about  two weeks and then disappears below the horizon for another two weeks before rising again.  At Full Earth time, the sun remains hidden around the lunar backside. When the nights are blackest, the bright ball of Earth spreads a welcome blue glow over the desolate landscape.

Earth covering the sun with a flash of the "diamond ring effect" just before total solar eclipse on April 15 and Oct. 8 next year. Stellarium
Simulated eclipse of the sun by the Earth just before totality on April 15 and Oct. 8 next year. On both dates, we’ll see a  total lunar eclipse from the ground.  Stellarium

Things really get interesting during lunar eclipses when the moon moves behind the Earth into the planet’s shadow. The next one’s on April 15, 2014. Here on the ground we’ll see the moon gradually munched into by Earth’s  shadow until totality, when sunlight from all the sunrises and sunsets around the rim of the planet are refracted by the atmosphere into the shadow, coloring the moon a coppery red.

Two pictures of the ring of sunset-sunrise fire around the Earth as it totally eclipsed the sun from the moon. Credit: NASA
Two pictures of the ring of sunset-sunrise fire around the Earth as it totally eclipsed the sun from the moon. Credit: NASA

Yutu will see just the opposite. Looking back toward the Earth from inside its shadow, the rover will witness a total eclipse of the sun by the Earth. If by some wonder the Chinese are able to photograph the event, we’ll see photos of the black ball of Earth rimmed in red fire from sunset and sunrise light refracted by our atmosphere. My interpretation using sky mapping software only hints at the wonder of the scene. Beijing Aerospace, if you’re reading this, please make it happen.


Earth eclipses the sun filmed by Japan’s Kaguya lunar orbiter. There are really two eclipses here – the Earth eclipsed by the limb of the moon at the video’s start followed by the solar eclipse.

On two other occasions, our robotic emissaries have photographed solar eclipses from Luna. NASA’s Surveyor 3 snapped a couple crude pictures of the April 24, 1967 eclipse from inside a crater in Mare Cognitium, the Sea that has Become Known. Japan’s orbiting Kaguya probe did the job much more eloquently on video during the February 9, 2009 penumbral lunar eclipse. In a penumbral eclipse (seen from Earth) the moon misses Earth’s dark inner shadow called the umbra, passing only through the outer penumbra, but because the Earth is three times larger than the sun (seen from the moon), it easily covered the sun completely in the complementary total solar eclipse.

And the best thing about watching eclipses from the moon? Guaranteed clear skies!

Smack! A New Crater Appears on the Moon/ Yutu Rover Update

Where there’s smoke, there’s fire, or in this instance, a new hole in the moon. NASA’s Lunar Impact Monitoring Program recorded the brightest meteoroid impact ever in its 8-year history on March 17 this year. The flash of light, as luminous as a 4th magnitude star and lasting about one second, was caught on video striking the moon in the Sea of Rains (Mare Imbrium) not far from the prominent crater Copernicus. Some time after the event, the Lunar Reconnaissance Orbiter (LRO) swept in for a closer look and spied a brand new impact crater. 

Since 2005 the program has detected over 300 flashes which are presumed to be from meteoroid impacts.

Bright impact flash made by a foot-wide rock that struck the moon on March 17, 2013. The moon was a crescent in the evening sky at the time. The impact occurred in the dark, earthlit part of the moon away from the sun-lit crescent. Click photo to see video about the event. Credit: NASA
Bright impact flash made by a foot-wide rock that struck the moon on March 17, 2013. The moon was a crescent in the evening sky at the time. The impact occurred in the dark, earthlit part of the moon away from the sun-lit crescent. Click photo to see video about the event. Credit: NASA

Based on the flash brightness and duration of the St. Pat’s Day smack, the space boulder measured between one to 1.5 feet long (0.3-0.4 meters) and struck the moon traveling at 56,000 mph with a force of 5 tons of TNT.  Scientists predicted then that the impact could produce a crater up to 65 feet (20 meters) in diameter.

Left: Fresh material brought to the surface makes the new 59-foot-wide crater look like it was spray painted white. Credit: NASA/GSFC/Arizona State University. Right: The meteoroid strike occurred near the prominent crater Copernicus in Mare Imbrium. Credit: Bob King
Left: Fresh material brought to the surface makes the new 59-foot-wide crater look like it was spray painted white. Credit: NASA/GSFC/Arizona State University. Right: The meteoroid strike occurred near the familiar crater Copernicus in the Sea of Rains (Mare Imbrium). Credit: Bob King

Well, guess what? When LRO dropped by for a look and compared images taken of the flash site before and after March 17. Staring it in the face was a brand new crater 59 feet across (18 meters). Wow! Just look at how reflective the crater and its rays of ejecta appear. That’s all unweathered, fresh dust and rock excavated from beneath the surface courtesy of 5 tons of extraterrestrial TNT. While impressive from LRO’s 31-mile altitude, the “St. Pat” crater is unfortunately invisible in even the largest telescopes from Earth.

Over time, cosmic rays, solar irradiation and micrometeoroids darken and redden the lunar soil. Millions of years from now, the once brilliant crater will blend into the moonscape. Can you imagine how bright larger craters like Tycho and Copernicus must have looked once upon a time?

Now it's the Chinese Yutu rover's turn to take a photo of the lander. Credit: CCTV
Now it’s the Chinese Yutu rover’s turn to take a photo of the lander. Credit: CCTV

The March 17 impact wasn’t the first new crater seen by LRO, but it does appear to be one of the largest. The LRO camera team has been systematically searching its archive of before and after images for many more lunar landscape changes. Some of those results – including these photos – were presented at the American Geophysical Union Fall Meeting last week; more new craters will be announced in the near future.

Left: The lander's new location in northern Mare Imbrium. Right: LRO scientists have so far nailed down the lander's  position somewhere inside the red box on the rim of a small crater with exposed rocky outcrops. Picture is about 1,750 feet side to side. Credit: NASA
Left: The lander’s new location in northern Mare Imbrium. Right: LRO scientists have so far nailed down the lander’s position somewhere inside the red box on the rim of a small crater with exposed rocky outcrops. Picture is about 1,750 feet side to side. Credit: NASA

While we’re on the topic of flyover discoveries, NASA will photograph the Chinese Yutu rover and lander when LRO orbits over western Mare Imbrium on Dec. 24 and 25. As it turns out, the lander didn’t land in Sinus Iridium as reported earlier but in nearby Mare Imbrium, a good distance east of the original site but still within the official “landing box”.

Fortuitously, this location turns out to be a great spot to examine young lavas not sampled during the Apollo missions. All the Apollo rocks ranged in age from 3.1 to 3.8 billion years old. Based on crater counts and the flow’s relatively fresh appearance, Yutu sits at the northern edge of a lava sheet dated at between 1 and 2.5 billion years. In lunar years, that’s fresh!

Flow lobes in the lavas of Mare Imbrium. Chang’e 3 landed at the extreme northern end of this sequence of lavas, which are very young in lunar terms. Credit: NASA / Apollo 15
Flow lobes in the lavas of Mare Imbrium. Chang’e 3 landed at the extreme northern end of this sequence of lavas, which are very young in lunar terms. Credit: NASA / Apollo 15

Younger flows experience less erosion, so the lunar bedrock isn’t buried beneath as much rock as at the Apollo sites. Where Yutu sits, the lunar soil or regolith goes down some 6-7 feet (2 meters) instead of 10-26 feet (3-8 meters) at other landing sites. That means easier excavation of much sought after lunar bedrock. We may even be seeing blocks of bedrock littered about the ~35 foot wide crater (10 meters) in one of the first photos sent back to Earth by the Chinese lander.

The boulders strewn about the crater rim at the Chang'e 3 landing site might be samples of lunar bedrock. Credit: CCTV
The boulders strewn about the crater rim at the Chang’e 3 landing site might be samples of lunar bedrock. Credit: CCTV

For a great analysis of the Chang’e 3 landing site, I recommend reading  A New Site to Explore on the Moon by lunar geologist Paul D. Spudis

Chinese rover & lander beam back Portraits with China’s Flag shining on Moon’s Surface

Yutu rover emblazoned with Chinese Flag as seen by the Chang’e-3 lander on the moon on Dec. 15, 2013. Notice the rover tire tracks left behind in the loose lunar topsoil. Credit: China Space
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China’s ambitious lunar space exploration program achieved another stunning success Sunday night, Dec 15, when the countries inaugural Chang’e-3 lunar lander and rover beamed back portraits of one another snapped from the Moon’s surface – that also proudly displayed the brilliant red Chinese national flag shining atop an extraterrestrial body for the very first time in human history.

“I announce the complete success of the Chang’e-3 mission,” said Ma Xingrui, chief commander of China’s lunar program, during a live CCTV broadcast as the portraits were shown to a worldwide audience from huge screens mounted at the mission control at the Beijing Aerospace Control Center (BACC) in Beijing.

Chinese President Xi Jinping was on hand to personally witness the momentous events in real time.

A wave of cheers and high fives rocked around mission control as the startling imagery of the ‘Yutu’ rover and Chang’e-3 lander nestled atop the Moon’s soil in the Bay of Rainbows was received around 11:42 p.m. Sunday, local Beijing time, 10:42 a.m. EST, via China’s own deep space tracking network.

Xi Jinping’s presence was a clear demonstration of China’s confidence in its lunar team and the importance of this space spectacular to China’s prestige and technological prowess.

China thus became only the 3rd country in the world to successfully soft land a spacecraft on Earth’s nearest neighbor after the United States and the Soviet Union.

China’s ‘Yutu’ rover had just rolled majestically onto the Moon’s soil hours earlier on Sunday, Dec. 15, at 4:35 a.m. Beijing local time – barely seven hours after the Chang’e-3 mothership touched down atop the lava filled plains of the Bay of Rainbows on Dec. 14.

The rover’s wheels left behind noticeable tire tracks as it drove across the loose lunar topsoil.

Read my earlier detailed accounts of the Dec. 15 drive by Yutu onto the lunar surface illustrated with an extensive photo gallery – here; and of the stunning Dec. 14 landing – here.

CCTV showed China’s President gleefully shaking hands and extending congratulations with many members of the mission team at BACC after seeing the high resolution photos of the Chang’e-3 rover emblazoned with China’s flag for himself.

Chang'e 3 lander as seen by the rover Yutu on the moon on Dec. 15, 2013.  Credit: China Space
Chang’e 3 lander as seen by the rover Yutu on the moon on Dec. 15, 2013. Credit: China Space

It’s been nearly four decades since the prior lunar landing was accomplished by the Soviet Union’s Luna 24 sample return spacecraft back in 1976.

America’s last visit to the Moon’s surface occurred with the manned Apollo 17 landing mission – crewed by astronauts Gene Cernan and Harrison ‘Jack’ Schmitt , who coincidentally ascended from the lunar soil on Dec. 14, 1972 – exactly 41 years ago.

“The Central Committee of the Communist Party and the Central Military Commission [responsible for China’s space program] sends congratulations to all the staff that participated in the successful completion of the mission and China’s first soft landing on the moon,” said the Chinese vice premier Ma Kai during the CCTV broadcast.

“The rover and lander are working properly and reaching the goals set.”

“Chang’e-3 is China’s most complicated space mission,” said Kai. “This shows China is dedicated to the peaceful uses of space.”

“There are many more complicated and difficult tasks ahead.”

Chang'e-3 lander imaged by the rover Yutu on the moon on Dec. 15, 2013.  Note landing ramp at bottom. Credit: CCTV
Chang’e-3 lander imaged by the rover Yutu on the moon on Dec. 15, 2013. Note landing ramp at bottom. Credit: CCTV

Indeed so far the Chang’e-3 mission has been primarily a highly successful demonstration of the extremely challenging engineering required to accomplish China’s first lunar landing.

Now the science phase can truly begin.

Over 4600 images have already been transmitted by Chang’e-3 since the Dec. 14 touchdown.

After rolling all six wheels into the dirt, Yutu – which translates as Jade Rabbit – drove to a location about nine meters north of the lander, according to CCTV commentators.

The rover then turned around so that the red Chinese flag emblazoned on the front side would be facing the lander’s high resolution color cameras for the eagerly awaited portraits of one another.

Yutu is nearly the size of a golf cart. It measures about 1.5 m x 1 m on its sides and stands about 1.5 m (nearly 5 feet) tall – nearly human height.

The 120 kg Yutu rover will now begin driving in a circle around the right side of the 1200 kg Chang’e-3 lander – for better illumination – at a distance ranging from 10 to 18 meters.

The rover will snap further photos of the lander as it traverses about from 5 specific locations – showing the front, side and back – over the course of the next 24 hours.

See the accompanying graphic – written in Chinese.

Yutu and the Chang'e 3 lander are scheduled to take photos of each other soon from locations outlined in this artists concept.  Credit: China Space
Yutu and the Chang’e 3 lander are scheduled to take photos of each other soon from locations outlined in this artists concept. Credit: China Space

Thereafter Yutu will depart the landing site forever and begin its own lunar trek that’s expected to last at least 3 months.

So the rover and lander will soon be operating independently.

They are equipped with eight science instruments including multiple cameras, spectrometers, an optical telescope, ground penetrating radar and other sensors to investigate the lunar surface and composition.

The radar instrument installed at the bottom of the rover can penetrate 100 meters deep below the surface to study the Moon’s structure and composition in unprecedented detail, according to Ouyang Ziyuan, senior advisor of China’s lunar probe project, in an interview on CCTV.

A UV camera will study the earth and its interaction with solar wind and a telescope will study celestial objects. This is done during the lunar day.

It will also investigate the moon’s natural resources for use by potential future Chinese astronauts.

China's first lunar rover separates from Chang'e-3 moon lander early Dec. 15, 2013. Screenshot taken from the screen of the Beijing Aerospace Control Center in Beijing. Credit: CCTV
China’s first lunar rover separates from Chang’e-3 moon lander early Dec. 15, 2013. Screenshot taken from the screen of the Beijing Aerospace Control Center in Beijing. Credit: CCTV

The two probes are now almost fully operational. Most of the science instruments are working including at least three cameras and the ground penetrating radar.

And although they have survived the harsh lunar environment thus far, they still face massive challenges. They must prove that they can survive the extremely cold lunar night and temperature fluctuations of more than 300 degrees Celsius – a great engineering challenge.

The rover will hibernate during the two week long lunar night.

A radioisotopic heater will provide heat to safeguard the rovers computer and electronics – including the alpha particle X-ray instrument on the rover’s robotic arm.

The Bay of Rainbows, or Sinus Iridum region, is located in the upper left portion of the moon as seen from Earth. You can see the landing site with your own eyes.

Chang’e 3 targeted lunar landing site in the Bay of Rainbows or Sinus Iridum
Chang’e 3 targeted lunar landing site in the Bay of Rainbows or Sinus Iridum

It was imaged in high resolution by China’s prior lunar mission – the Chang’e-2 lunar orbiter and is shown in graphics herein.

China’s Chang’e-3 probe joins NASA’s newly arrived LADEE lunar probe which entered lunar orbit on Oct. 6 following a spectacular night time blastoff from NASA’s Wallops Flight Facility in Virginia.

Stay tuned here for Ken’s continuing Chang’e-3, LADEE, MAVEN, MOM, Mars rover and more news.

Ken Kremer

China's first lunar rover separates from Chang'e-3 moon lander early Dec. 15, 2013. Screenshot taken from the screen of the Beijing Aerospace Control Center in Beijing. Credit: Xinhua/post processing by Marco Di Lorenzo/Ken Kremer
China’s first lunar rover separates from Chang’e-3 moon lander early Dec. 15, 2013. Screenshot taken from the screen of the Beijing Aerospace Control Center in Beijing. Credit: Xinhua/post processing by Marco Di Lorenzo/Ken Kremer

Chinese ‘Jade Rabbit’ Rover Aims For The Moon On Sunday

If all goes well, expect another moon robot very soon. The Yutu (“Jade Rabbit”) rover will lift off from China as a part of the Chang’e-3 mission — target launch date Sunday (Nov. 29) — to explore the moon’s Sea of Rainbows after its scheduled landing two weeks later, Dec. 14.

There are other spacecraft orbiting the moon — including the newly launched LADEE from NASA, which is checking out the moon’s tenuous atmosphere — but if this mission succeeds, it would be the first soft landing since Russia’s Luna-24 in 1976. That’s a 37-year drought.

Recent English information on the mission is scarce, but it’s been widely reported that the mission will include a lander in a six-wheeled rover. This Chinese news agency notes that planners expect to put up an astronomical telescope, test remote control between the moon and the Earth, and explore areas around the landing location. You can also read (dated) background information on the mission on the Chinese National Space Administration’s website.

A 50-foot (15-meter) tracking dish at the European Space Agency's tracking station at Kourou, French Guiana. In the background is the successful Herschel and Planck launch of May 14, 2009. Credit: ESA/A. Chance
A 50-foot (15-meter) tracking dish at the European Space Agency’s tracking station at Kourou, French Guiana. In the background is the successful Herschel and Planck launch of May 14, 2009. Credit: ESA/A. Chance

The European Space Agency (ESA), meanwhile, released a press update describing how people from its organization will help track the mission during its journey to the moon. The Europeans will be helping the Chinese track the mission all the way to the time it is expected to reach the surface. After the mission lands, ESA will use two antennas to perform a measurement intended to figure out — “with extreme accuracy”, the agency says — where the lander is located.

And for those who remember, a fun bit of history from 1969 recalled by the Planetary Society: during Apollo 11, the first manned mission to land on the moon, this ground-to-moon exchange actually happened:

Capcom: Roger. Among the large headlines concerning Apollo this morning, there’s one asking that you watch for a lovely girl with a big rabbit. An ancient legend says a beautiful Chinese girl called Chang-o has been living there for 4,000 years. It seems she was banished to the Moon because she stole the pill of immortality from her husband. You might also look for her companion, a large Chinese rabbit, who is easy to spot since he is always standing on his hind feet in the shade of a cinnamon tree. The name of the rabbit is not reported.

Buzz Aldrin, slated to be second man on the moon: Okay. We’ll keep a close eye out for the bunny girl.