South Korea is scouting out the moon, with more missions to come

A control room briefing at the Korean Aerospace Research Institute prior to launch of the Danuri, in Daejeon, South Korea. PHOTO: NYTIMES

SEOUL (NYTIMES) - South Korea set off for the moon on Thursday (Aug 4). But it doesn't want to stop there.

"We are also considering using the moon as an outpost for space exploration," Mr Kwon Hyun Joon, director-general of space and nuclear energy at South Korea's Ministry of Science, said in a written response to questions.

"Although we hope to explore the moon itself, we also recognise its potential to act as a base for further deep space exploration such as Mars and beyond," he said.

South Korea's lunar spacecraft, named Danuri, was launched on a SpaceX Falcon 9 rocket from Florida, setting out on a roundabout but fuel-efficient path that would have it arriving at the moon in mid-December. There, it would begin an orbit at an altitude of 100km above the moon's surface.

The main mission is scheduled to last for one year.

Originally known as the Korea Pathfinder Lunar Orbiter, the mission was given the name Danuri after it became the winning entry in a naming contest. It is a portmanteau of the Korean words for "moon" and "enjoy."

Mission's goals

Danuri will join spacecraft from Nasa, India and China that are currently exploring Earth's companion.

Much like the United Arab Emirates (UAE), which launched towards Mars on a Japanese rocket in 2020, South Korea is the latest country with a small but ambitious space programme to set out on a beyond low-Earth orbit.

And also like the UAE's Hope orbiter, the Danuri mission is intended to make meaningful scientific contributions to global efforts to explore and understand the solar system.

Mr Kwon said the main goal of the Danuri mission was to develop basic technologies like the design of orbital trajectories, deep space navigation, a high-thrust propulsion system and a 35m antenna to communicate with distant spacecraft.

But the spacecraft's scientific payload is sophisticated and will aid scientists in South Korea and globally in studying the moon's magnetic field, measuring its quantities of elements and molecules like uranium, water and helium-3 and photographing the dark craters at the lunar poles, where the sun never shines.

In addition to providing one of the instruments, called ShadowCam, Nasa chose nine scientists to participate on Danuri.

Probing magnetic field

One of its most important scientific instruments is a magnetometer. The moon's interior no longer generates a magnetic field, but it once did, and that primordial field is preserved in lava flows that hardened during this era.

Dr Ian Garrick-Bethell, a professor of planetary science at the University of California, Santa Cruz and a participating scientist on the Danuri mission, said that the early magnetic field appears to have been surprisingly strong - potentially even as much as double the strength of Earth's current magnetic field.

The 35m deep space antenna in Yeoju, South Korea, that communicates with the Danuri. PHOTO: NYTIMES

Dr Garrick-Bethell said it was puzzling that "such a small little iron core could have generated such a strong magnetic field".

He is hoping that after the spacecraft's primary mission of one year is complete, South Korea could choose to move Danuri much closer to the moon's surface, within 19km or less, where the magnetometer could get a much better look at the magnetised rocks.

"Even a few passes at those low altitudes could help constrain how strongly magnetised those rocks are," he said.

Dr Garrick-Bethell is also looking to use the magnetometer to study magnetic fields generated within the moon as it is buffeted by the solar wind, a stream of charged particles emanating from the sun.

The rise and fall in the strength of the magnetic field in the solar wind induces electric currents in the moon, and those electric currents in turn generate magnetic fields that will be measured by Danuri.

The characteristics of the magnetic field will give hints of the structure and composition of the moon's interior.

Deep-space missions

Final inspections at the facility before it was shipped to Florida. PHOTO: NYTIMES

Scientists will use another of Danuri's instruments, a gamma-ray spectrometer, to measure quantities of different elements on the moon's surface.

Danuri's device can pick up a wider spectrum of lower energy gamma rays than similar instruments on earlier lunar missions, "and this range is full of new information to detect elements on the moon", said Dr Naoyuki Yamashita, a New Mexico-based scientist who works for the Planetary Science Institute in Arizona. He is also a participating scientist on Danuri.

Dr Yamashita is interested in radon, which forms from the decay of uranium. Because radon is a gas, it could travel from the moon's interior to its surface. (This is the same process that sometimes causes the build-up of radon, which is also radioactive, in the basements of houses.)

The amounts of the radioactive elements could provide a history explaining when various parts of the moon's surface cooled and hardened, Dr Yamashita said, helping scientists to work out which of the moon's lava flows are older or younger.

The Korean Aerospace Research Institute, South Korea's equivalent of Nasa, will use Danuri's high-resolution camera to scout the lunar surface for potential sites for a robotic lander mission in 2031, Dr Kwon said.

A second camera will measure polarised sunlight bouncing off the lunar surface, revealing details about the size of particles that make up the lunar soil.

Because constant bombardment by solar wind, radiation and micrometeorites breaks the soil apart, the size of grains found in a crater could give an estimate of its age. (Smaller grains would suggest an older crater.)

The polarised light data will also be used to map abundances of titanium on the moon, which could one day be mined for use on Earth.

Promise of ice

Nasa supplied one of the cameras, a ShadowCam, which is sensitive enough to pick up the few photons that bounce off the terrain into the moon's dark, permanently shadowed craters.

These craters, located at the moon's poles, remain forever cold, below minus 149 deg C, and contain water ice that has accumulated over the aeons. The ice could provide a frozen history of the 4.5 billion year old solar system.

It could also be a bounty of resources for future visiting astronauts. Machinery on the moon could extract and melt the ice to provide water. That water could then be broken apart into oxygen and hydrogen, which would provide both air to breathe for astronauts and rocket propellants for travellers seeking to travel from the moon to other destinations.

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