The Earth and Moon shared the same magnetic field some 3.5 billion to 4.1 billion years ago, and the Moon’s field helped shield the Earth from solar radiation that might have stripped away its atmosphere, concludes a NASA-led study published in the journal Science Advances.
“The Moon seems to have presented a substantial protective barrier against the solar wind for the Earth, which was critical to Earth’s ability to maintain its atmosphere during this time,” said Jim Green, NASA’s chief scientist and lead author of the study, as reported by Business Insider India.
The scientists created a computer model to simulate the behavior of the magnetic fields of the two orbs. The magnetospheres of the Moon and Earth would have been magnetically connected in the polar regions of each body. At certain times, the Moon’s magnetosphere would have served as a barrier to harsh solar radiation bombarding the Earth-Moon system.
The model also suggests that there was some atmospheric exchange as well. The Sun’s radiation would have charged neutral particles in the Earth’s upper atmosphere, enabling them to travel to the Moon along the lunar magnetic lines. The process might have contributed to the Moon maintaining a thin atmosphere, including nitrogen.
As the Moon cooled and lost its magnetosphere, solar wind stripped the atmosphere away.
Radiation will be a major hazard of living on the Moon, especially for anyone not behind protective shielding. The release of energy from solar flares has been difficult to forecast. Now four Japanese scientists with Nagoya University and the National Astronomical Observatory of Japan have developed a model, based on observations of the sun from 2008 to 2018, for predicting large solar flares. In an article published in Science, they say that “in most cases” the model correctly identifies the region of the sun that will produce large flares within 20 hours and, within limits, how powerful it will be.
However, say the authors, the model does produce some false positives and false negatives. “Accurate predictions of solar flares could improve forecasts of space weather conditions around Earth,” they say. Presumably, those predictions apply to the Moon as well. Here is the abstract for the paper in Science.
Solar flares are highly energetic events in the Sun’s corona that affect Earth’s space weather. The mechanism that drives the onset of solar flares is unknown, hampering efforts to forecast them, which mostly rely on empirical methods. We present the κ-scheme, a physics-based model to predict large solar flares through a critical condition of magnetohydrodynamic instability, triggered by magnetic reconnection. Analysis of the largest (X-class) flares from 2008 to 2019 (during solar cycle 24) shows that the κ-scheme predicts most imminent large solar flares, with a small number of exceptions for confined flares. We conclude that magnetic twist flux density, close to a magnetic polarity inversion line on the solar surface, determines when and where solar flares may occur and how large they can be.
The Parker Solar Probe has yielded considerable insight into the formation and structure of solar winds, providing scientists that hopefully will help them better predict when mammoth ejections of solar material will occur. Coronal mass ejections can disable communications and defense satellites and can harm astronauts outside of Earth’s protective electromagnetic field.
Launched in August 2018, the probe has passed closer to the sun than at any previous spacecraft in history. The vessel is equipped with a suite of high-tech instruments engineered to withstand the sun’s blistering heat — it will pass within 15 million miles of the sun, compared to the 36 million miles of Mercury’s orbit. Instruments include five antennas, an image maker, and devices that measure the energies of different particles.
The mission’s goal is to “understand the sources and structure of the solar wind up close right as it leaves the sun,” said physicist Stuart Bale of the University of California-Berkeley, in the press conference reported by Popular Mechanics. “What Parker has done has got us closer than ever to the Sun and now we can really see a lot of structure and we can see in this case we can clearly see a source of the wind.”
The Moon may not have an atmosphere, but it does have “weather” after a fashion. Researchers have found that the particles in solar wind appear to interact with the Moon in an unexpected way, reports the Daily Mail.
The solar particles interact with the Earth’s magnetic field to create the aurora borealis. But the Moon lacks a magnetic field, so scientists thought it passively absorbed the solar wind. But measurements made by Indian’s Chandrayaan-1 lunar orbiter have revealed that 10% of the solar wind is reflected back into space, creating turbulence as solar wind streams past the Moon. Vortexes billow onto the dark side of the Moon.
Charles Lue, a researcher at the Swedish Institute of Space Physics, has found that the reflection of solar wind varies with localized magnetic fields on the lunar surface.
Explains the Daily Mail:
In areas with strong magnetism, caused by iron in the crust, the solar wind flow is restricted, while adjacent areas receive increased flow. This results in unusual spirals of ions streaming off the dayside of the moon, where the solar wind strikes first, to the nightside.
The weathering of the moon’s surface by the solar wind may be less than previously predicted, which could mean there is less water hidden beneath the crust. Said Lue: “The reduced solar wind weathering allows us to separate micro-meteorite and solar wind-inducing weathering, including the effects of different solar wind species, differently well shielded.”
The Moon’s thin atmosphere contains neon, NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft has confirmed.
“The presence of neon in the exosphere of the moon has been a subject of speculation since the Apollo missions, but no credible detections were made,” said Mehdi Benna of NASA’s Goddard Space Flight Center in Greenbelt, Maryland and the University of Maryland, Baltimore County in a NASA press release. “We were very pleased to not only finally confirm its presence, but to show that it is relatively abundant.”
Because the Moon’s atmosphere is so tenuous, about 100 trillion times less dense than Earth’s atmosphere are sea level, the volume of neon is minute.
Most of the gases in the exosphere — primarily neon, argon, and helium — comes from the solar win, a stream of electrically conducting gas blown from the surface of the sun into space at about one million miles per hour. All of these elements impact the Moon, but only helium, neon and argon are volatile enough to return to space. A portion of the helium, argon, and neon in the lunar exosphere comes from naturally occurring radioactive potassium-40, thorium, and uranium found naturally in lunar rocks. more “Neon Found in Lunar Atmosphere”