China's Yutu 2 rover finds 'milestone' on far side of the moon

China's Chang'e 4 spacecraft are back in action for a 27th lunar day on the far side of the moon, but it's the discoveries from the mission's previous lunar day that have scientists excited. The Chang'e 4 lander and Yutu 2 rover resumed activities on Feb. 6 after hibernating during the severe cold of lunar night, according to the Chinese state-run media outlet Xinhua. But one lunar day earlier the rover came across a curious rock specimen which the Yutu 2 drive team began to refer to as a "milestone." According to a Yutu 2 diary published by Our Space, the Chinese language science outreach channel affiliated with the China National Space Administration (CNSA), mission scientists agreed with the drive team that the elongated rock was worth closer inspection. The team then planned to do a close approach and analyze the rock with Yutu 2's Visible and Near-infrared Imaging Spectrometer (VNIS) instrument, which detects light that is scattered or reflected off materials to reveal their makeup. VNIS has been used to investigate a number of rocks and regolith samples along Yutu 2's path across Von Kármán crater. These include unusual melt glass specimens and potentially material from the lunar mantle. While not looking particularly exciting to the untrained eye, the find has generated interest among lunar scientists. "It seems to have a shard-like shape and is sticking out of the ground. That's definitely unusual," Dan Moriarty, NASA Postdoctoral Program Fellow at the Goddard Space Flight Center in Greenbelt, Maryland, told Space.com.

This photo taken by China's Yutu 2 moon rover shows the elongated "milestone" rock on the lunar surface.

(Image: © CNSA)

"Repeated impacts, stresses from thermal cycling, and other forms of weathering on the lunar surface would all tend to break down rocks into more-or-less 'spherical' shapes, given enough time," Moriarty said. "Think of how rocky beaches wear down stones to smooth, round shapes over time by repeated jostling in the waves."

Moriarty said both the shard-like shape and that pronounced "ridge" running near the edge of the rock seem to indicate that this rock is geologically young, and was emplaced relatively recently.

"Milestone" rock, China's Yutu 2 rover image

"I would definitely guess an origin as impact ejecta from some nearby crater. It is possible that a rock with this aspect ratio could have been produced by a process known as spallation, where intact fragments of rock are blown off the nearby surface without experiencing the same degree of shock pressures that the immediate target undergoes," Moriarty said, adding that this initial assessment is just a guess.

Followup detections and data from VNIS will provide much greater insight. Clive Neal, a leading lunar expert at the University of Notre Dame, agrees that, based on the images, the specimens are impact ejecta rather than exposed bedrocks. "The question I have is are they locally derived? Hopefully the spectral data will allow an evaluation of the origin as local or exotic, that is, from outside this area," he said.

Yutu 2 and the Chang'e 4 lander have already greatly exceeded their design lifetimes of 90 Earth days and one year, respectively. The rover has covered a total of 2,060 feet (628 meters) since its deployment from the lander on Jan. 3, 2019.


In November last year China launched its Chang'e 5 lunar sample return mission. The mission resulted in 3.81 lbs. (1.73 kilograms) of fresh moon samples being delivered to Earth just over three weeks later. CNSA last month published procedures for requesting samples for scientific analysis.

First private spacecraft shoots for the moon

"Moon of Israel" is an epic 1924 film from the golden era of silent movies, and helped launch the directing career of Michael Curtiz, of "Casablanca" fame. Sequels seldom live up to the original. But if Israel's plans to put a robotic lander on the moon in February 2019 can be considered a sequel, this new "Moon of Israel" mission, led by the nonprofit company SpaceIL, will be a blockbuster in its own right. Lunar landings date back to the 1960s. The United States landed 12 people on six separate occasions as part of the Apollo program, along with robotic spacecraft such as Surveyor, which served as a precursor to human missions. The Soviet Union preformed robotic Luna missions and landed Lunokhod automated rovers in the 1970s. Most recently China landed the Chang'e 4 robotic probe on the back side of the moon. These missions are all amazing technical accomplishments, and marvels of human know-how, sponsored and built by large government space agencies. The moon's next visitor is different. SpaceIL's Beresheet - Hebrew for "In the Beginning" - will become the first privately funded mission to launch from Earth and land on the moon, and the first spacecraft to propel itself over the lunar surface after landing by "hopping" on its rocket engine to a second landing spot. The mission marks yet another milestone, not only in the history and technical arc of space exploration, but also in how humankind goes about space exploration.

SpaceIL was founded in 2011 to compete in the Google Lunar XPrize, a program that planned to award US$30 million to the first privately funded team who could build a spacecraft and land it successfully on the moon.

Beyond landing, the spacecraft, or a rover, had to travel a distance of 500 meters or more and beam high-definition imagery of the landing environment to Earth. The Google Lunar XPrize contest deadline ended in 2018 without a winner. Undaunted, SpaceIL forged ahead with the development and construction of the spacecraft, and is now ready to launch from Cape Canaveral, Florida.

The Beresheet lander is about the size and shape of a family dinner table, roughly 6 feet in diameter and 4 feet high, weighing (on Earth) about 350 pounds. This doesn't include the nearly 1,000 pounds of fuel needed to land the spacecraft on the moon. Carrying instrumentation to measure the magnetic field of the moon, a laser-reflector provided by NASA and a time-capsule of cultural and historical Israeli artifacts, the mission will ride into space as a secondary payload - like a rideshare passenger - aboard a SpaceX Falcon 9 rocket.

Going to the moon, without a rocket

The primary cargo on the SpaceX launch is not the SpaceIL lander, but instead a communications satellite for delivery a very high Earth-centered, geostationary orbit approximately 22,000 miles above the Earth's equator.

This effectively parks the communications satellite above a fixed point on the Earth, its orbit synchronized precisely with our planet's daily rotation. The Beresheet spacecraft will accompany the primary satellite on its journey. But in order to reach the moon, it needs to travel more than 10 times farther.

In spaceflight, the primary constraint in traveling from place to place is not distance, but the quantity of energy required. The Falcon 9 rocket only carries Beresheet about 10 percent of the total distance to the moon.

But it provides nearly 90 percent of the total energy required to get there. Consequently, once lifted from the surface of the Earth, and with a small amount of additional energy from its own propulsion system, Beresheet can boost its own orbit by positioning itself so that it's captured by the moon's gravitational pull. This process will take several weeks.

Once landed on the moon, however, the mission may only last a few more days. The lander is not designed for the long haul, but instead will demonstrate advances in technology as well as the business model for a privately funded spacecraft landing on another body in the solar system. In this sense, Beresheet will create a second and even more memorable "Moon of Israel."

There is no air on the moon - and therefore also no sound. So, like the original 1924 film, this sequel will also be silent. But the participants are not actors, and the view will be in high-definition color.

The technical know-how developed by the engineering team, the scientific and technical data from the spacecraft's instruments, learning how spaceflight missions can be executed outside of a government program, and the inspiration provided for an entire generation of young people - especially in Israel and the Middle East region - will all bring valuable insights and inspiration for decades to come.