### Recent Lunar Volcanism: An Unexpected Revelation
The Moon, the nearest celestial body to Earth, has captivated researchers and enthusiasts alike for ages. Its terrain, characterized by extensive plains referred to as “maria,” narrates the tale of primordial volcanic activity that sculpted its surface eons ago. Yet, fresh discoveries from China’s Chang’e-5 mission have introduced an unexpected chapter in the Moon’s geological narrative: signs of volcanic activity that transpired much more recently than earlier assumptions suggested.
#### The Age-Old Volcanic Legacy
The somber plains, or “maria,” observable on the Moon’s surface are the vestiges of colossal volcanic eruptions that transpired early in its history. These events, which released immense quantities of basaltic lava, are thought to have ceased around 3 billion years ago. For an extended period, experts held that this indicated the conclusion of significant volcanic events on the Moon. Nevertheless, minor volcanic activities could have persisted until roughly 2 billion years ago, as indicated by samples gathered from various lunar missions, including both the Apollo missions and, more recently, China’s Chang’e-5 endeavor.
#### Indications of Contemporary Volcanism
Although most volcanic activity on the Moon is ancient, there are indications that smaller eruptions might have taken place more recently. Data from lunar orbiters have pinpointed regions of the Moon’s surface that seem to be results of volcanic processes, characterized by a scarcity of impact craters, suggesting a younger age. However, these findings have been tinged with skepticism, as accurately determining the timing and scale of these occurrences proved challenging.
The Chang’e-5 mission, which successfully retrieved samples from the Moon in 2020, has shed new light on this enigma. Among the collected materials were diminutive, glassy beads formed from liquefied substances. These beads, attributable to both volcanic eruptions and impact events, have garnered close scientific examination as researchers strive to decipher their origin.
#### The Difficulty of Recognizing Volcanic Beads
Identifying volcanic beads among the myriad samples collected by Chang’e-5 was a daunting challenge. The Moon is perennially bombarded by space particles, from minuscule dust flecks to larger meteoroids. These collisions generate sufficient heat to melt the lunar crust, thus creating glassy beads. Therefore, most of the beads gathered by Chang’e-5 are probably products of impact events rather than volcanic sources.
To discern the volcanic beads, scientists implemented a systematic procedure. Initially, they excluded any beads with mixed compositions, such as those containing unmelted fragments or exhibiting clear compositional discrepancies. This process reduced the candidate volcanic beads from over 3,000 to 764. Subsequently, the remaining beads were subjected to analysis via an electron probe microanalyzer, which bombards samples with electrons and measures the released photons to identify the present elements.
Guided by the composition of volcanic rocks retrieved during the Apollo missions, the researchers situated their focus on beads exhibiting a high magnesium oxide content in relation to calcium and aluminum oxides. This further refined their selection to 13 potential volcanic candidates. The concluding phase involved analyzing the sulfur isotopes within the beads, as impact melting typically alters sulfur isotope ratios compared to unaltered lunar rocks. After diligent assessment, only three beads surfaced as likely of volcanic origin.
#### An Unexpected Revelation
The three volcanic beads underwent uranium-based radioactive dating, unveiling an astonishing finding: these beads were formed during an eruption estimated to have occurred approximately 123 million years ago, with a margin of error of 15 million years. This revelation bears great significance, as it implies that volcanic activity on the Moon continued far longer than previously acknowledged. Prior to this, the last confirmed eruptions were thought to have transpired around 2 billion years ago.
This discovery invites compelling inquiries regarding the Moon’s thermal evolution. Over millions of years, the Moon has considerably cooled, increasing the distance between its crust and any residual molten material within its core. This cooling trend should have rendered volcanic activity increasingly improbable. So, what might have triggered this relatively recent eruption?
One hypothesis involves a substance known as KREEP (potassium, rare earth elements, and phosphorus), which is abundant in radioactive isotopes. Such isotopes could induce localized heating, potentially prompting volcanic occurrences in specific regions of the Moon. However, without additional data, determining the precise cause of the eruption remains elusive.
#### The Horizon of Lunar Exploration
The identification of recent volcanic activities on the Moon serves as a reminder of the evolving nature of our understanding of this celestial neighbor. The Chang’e-5 mission has yielded invaluable new insights, yet numerous questions persist. For instance, the precise location of the eruption that created the volcanic beads is still undetermined. The beads might have traversed substantial distances in the Moon’s weak gravitational field and could have been further dispersed due to later impacts.
As we progress in lunar exploration,
