South Korea went to the moon on Thursday. But it doesn’t want to stay that way.
“We are also considering using the moon as an outpost for space exploration,” said Kwon Hyun-joon, director-general of space and nuclear energy at South Korea’s science ministry, in a written response to questions. “While we hope to explore the moon itself, we also recognize its potential to act as a base for further exploration of space such as Mars and beyond.”
South Korea’s lunar spacecraft, dubbed Danuri, was launched on a SpaceX Falcon 9 rocket from Florida and embarked on a circuitous but fuel-efficient path that will reach it on the moon in mid-December. There it will begin an orbit at an altitude of 62 miles above the lunar surface. The main mission is designed for one year.
Originally known as the Korea Pathfinder Lunar Orbiter, the mission was named Danuri after winning a naming contest. It is a portmanteau of the Korean words for “moon” and “enjoy”.
Mr. Kwon said the main goal of the Danuri mission is to develop fundamental technologies such as orbit design, space navigation, a high-thrust propulsion system and a 35-meter antenna to communicate with distant spacecraft.
But the spacecraft’s science payload is sophisticated and will help scientists in South Korea and around the world study the moon’s magnetic field, measure its amounts of elements and molecules like uranium, water and helium-3, and photograph the dark craters at the lunar poles. where the sun never shines. In addition to providing one of the instruments, called ShadowCam, NASA selected nine scientists to participate in Danuri.
One of their most important scientific instruments is a magnetometer. The moon’s interior no longer generates a magnetic field, but it used to, and this original field is preserved in lava flows that hardened during this era.
Ian Garrick-Bethell, a professor of planetary sciences at the University of California, Santa Cruz and a scientist involved in the Danuri mission, said the early magnetic field appears to have been surprisingly strong — possibly even twice that of Earth’s current magnetic field.
dr Garrick-Bethell said it was puzzling that “so small a little iron core could have created such a powerful magnetic field.”
He hopes that after completing the spacecraft’s main year-long mission, South Korea might decide to bring Danuri much closer to the lunar surface, within 12 miles or less, where the magnetometer could get a much better view of the magnetized rocks.
“Even a few passes at these low elevations could help limit the magnetization of these rocks,” he said.
dr Garrick-Bethell also wants to use the magnetometer to study magnetic fields created in the Moon as it is shaken by the solar wind, a stream of charged particles emanating from the Sun.
The rise and fall in strength of the magnetic field in the solar wind induces electric currents in the moon, and these electric currents in turn create magnetic fields measured by Danuri. The properties of the magnetic field provide clues to the structure and composition of the lunar interior.
This work also requires combining measurements from two NASA spacecraft, THEMIS-ARTEMIS P1 and P2, traveling around the moon in highly elliptical orbits so they can measure the changes in the solar wind, while Danuri measures the induced magnetic fields more closely the Surface.
“What we would learn from this is a kind of global map of the internal temperature and possibly the composition and maybe even the water content of the deep parts of the moon,” said Dr. Garrick-Bethel.
The scientists will use another of Danuri’s instruments, a gamma-ray spectrometer, to measure the amounts of different elements on the lunar surface. Danuri’s device can pick up a broader spectrum of lower-energy gamma rays than similar instruments on previous lunar missions, “and this spectrum is loaded with new information for detecting elements on the moon,” said 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 is produced when uranium decays. Since radon is a gas, it could reach its surface from inside the moon. (This is the same process that sometimes leads to the accumulation of radon, which is also radioactive, in the basements of houses.)
The levels of radioactive elements could provide a history that explains when different parts of the moon’s surface cooled and hardened, said Dr. Yamashita and helped scientists figure out which of the moon’s lava flows are older or younger.
The Korean Aerospace Research Institute, South Korea’s NASA counterpart, will use Danuri’s high-resolution camera to explore the lunar surface for potential locations for a robotic lander mission in 2031, Mr. Kwon said.
A second camera measures polarized sunlight reflected off the lunar surface, revealing details about the size of the particles that make up the lunar soil. As constant bombardment from solar wind, radiation, and micrometeorites breaks up the ground, the size of grains found in a crater could provide an estimate of its age. (Smaller grains would indicate an older crater.)
The polarized light data is also being used to map titanium deposits on the moon that could one day be mined for use on Earth.
NASA provided one of the cameras, a ShadowCam, sensitive enough to catch the few photons that bounce off the terrain into the moon’s dark, permanently shadowed craters.
Located at the moon’s poles, these craters remain cold forever, below minus 300 degrees Fahrenheit, and contain water ice that has accumulated over the eons.
The ice could provide a frozen history of the 4.5 billion year old solar system. It could also be a wealth of resources for future astronauts. Machines on the moon could extract and melt the ice to provide water. This water could then be broken down into oxygen and hydrogen, which would provide air for astronauts to breathe and rocket fuel for travelers wanting to travel from the moon to other destinations.
One of ShadowCam’s main purposes is to find the ice. But even with Danuri’s sophisticated instruments, that could be a challenge. Shuai Li, a researcher at the University of Hawaii and a scientist involved in Danuri, thinks the concentrations may be so small that they aren’t obviously brighter than areas with no ice.
“If you don’t look at it carefully, you might not be able to see it,” said Dr. Li
Jean-Pierre Williams, a planetary scientist at the University of California, Los Angeles, and another scientist involved in the Danuri mission, hopes to create detailed temperature maps of the craters by combining the ShadowCam imagery with data collected from the Lunar Reconnaissance NASA orbiters were collected.
NASA’s orbiter, which has been studying the moon since 2009, carries an instrument that records lunar surface temperatures. But those measurements are blurry over a fairly large area, about 900 feet wide. The resolution of a ShadowCam is about 5 feet per pixel. ShadowCam images used in conjunction with computer models could make it possible to tease out temperature fluctuations on the surface.
“With this data, we can map local and seasonal temperatures,” said Dr. Williams. This, in turn, can help scientists understand the stability of water and carbon dioxide ice in the crater.
Researchers have to wait several months for the science to begin. The spacecraft takes a long, energy-efficient route to the moon. It will first head for the Sun and then loop back to be captured in lunar orbit on December 16th. This “ballistic trajectory” takes longer but doesn’t require a large engine fuse to slow the spacecraft when it reaches the moon.
South Korea has an extensive military missile program and has placed several communications and Earth observation satellites in low Earth orbit since launching its first in 1992. Also, it has expanded its domestic rocket launch capabilities, so future missions may not depend on SpaceX or other countries to get into space. In June, the Korean Aerospace Research Institute successfully launched several satellites into orbit with the second flight of its home-developed Nuri rocket.
“We will take on challenging projects like lunar landers and asteroid exploration,” Mr. Kwon said.
Jin Yu Young contributed reporting from Seoul.