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A NASA spacecraft charting the topography of the moon in exceptional detail has produced a catalogue of lunar craters that traces billions of years of impact history on the moon. The cratering record on the moon provides a proxy for similar impacts by interplanetary debris such as comets and asteroids on Earth, the effects of which have largely been erased by billions of years of erosion and geologic activity.
The Lunar Orbiter Laser Altimeter (LOLA), one of seven instruments that have circled the moon since June 2009 on board the Lunar Reconnaissance Orbiter (LRO), bounces a laser beam off the lunar surface and times its return to gauge the elevation of the terrain below. Fifty kilometers above the moon, LOLA can pinpoint the elevation of lunar landforms to within 10 centimeters.
A new study based on more than two billion laser readings taken as LRO cruised through its orbit has provided what may be the most complete accounting of lunar craters yet. The research appears in the September 17 issue of Science.
The researchers used LOLA's topography to identify more than 5,000 craters on the lunar surface, restricting the search to craters 20 kilometers in diameter and larger. The crater catalogue roughly doubles the size of that produced in 1978 by Don Wilhelms of the U.S. Geological Survey and his colleagues using photographs from NASA's Lunar Orbiter missions in the mid-1960s. The 20-kilometer-size cutoff was primarily set for the sake of expediency, as each crater must be manually counted. "At some point you would be doing nothing but counting craters for the rest of your life," says James Head, a planetary geoscientist at Brown University and the lead author of the study.
Previous crater counts had relied on less uniform data, including collections of photographs taken at different lighting angles that changed the craters' shadow profiles. But the new study's use of a single laser range finder means the results are not dependent on lighting or on differences between instruments. "It's a very useful contribution in the sense that it's the first time a hom*ogeneous data set of the entire moon, front and back, has been examined from the point of view of crater distribution," says Jay Melosh, a planetary scientist at Purdue University who did not contribute to the new research.
With that data set, Head and his colleagues were able to determine which areas are truly ancient and which have been resurfaced relatively recently in lunar history. Lava flows three billion or four billion years ago, for instance, flooded lunar plains and filled craters there, whereas large impacts excavated vast amounts of lunar material that fell to the surface, burying or obscuring nearby craters.
The researchers found that large impactors, in addition to excavating huge basins, sprayed ejecta over vast swaths of the lunar surface. The impact that formed a large basin known as Orientale in the western area of the moon's near side, which the group investigated in detail, obliterated all prior craters within the basin itself, an area of nearly 700,000 square kilometers. But it also overwrote parts of the cratering record up to 500 kilometers away from the basin, reducing crater counts over an area of roughly three million square kilometers, or about 8 percent of the lunar surface. And, Head notes, Orientale is not even the biggest lunar basin—a larger impact such as the one that formed the Imbrium Basin would affect an even larger fraction of the terrain.
The crater map derived from LOLA data also confirms an idea put forth in 2005 by Robert Strom of the University of Arizona and his colleagues: that a shift in the impactor population took place around 3.8 billion years ago, around the time that Orientale Basin was excavated. The proportion of large (50- to 100-kilometer) craters is greater in the relatively ancient lunar highlands than in the younger lava plains, implying that the moon was pelted by two different populations of impactors in its history, the latter of which had fewer large bodies. One explanation for such a transition would be an orbital migration of the giant planets that disrupted the asteroid belt, sending a slew of rocky bodies flying toward Mars, Mercury, Venus, Earth and its moon early on.
Studying the craters on the moon offers a window into that violent history of the young solar system that is not nearly as accessible on Earth. "This all has implications for the Earth," Head says. "The Earth's record is abysmal back then because it's such a dynamic planet."
FAQs
Lunar topography
The Moon has been measured by the methods of laser altimetry and stereo image analysis, including data obtained during several missions. The most visible topographical feature is the giant far-side South Pole-Aitken basin, which possesses the lowest elevations of the Moon.
What are the impact craters on the surface of the Moon? ›
Craters are the most common surface features on many solid planets and moons—Mercury and our Moon are covered with craters. This portion of the Moon is covered by numerous circular holes. These are impact craters, each of which was formed when an asteroid or comet collided with the Moon's surface.
What type of erosion impacts the Moon? ›
The most significant kind of erosion that occurs on the Moon today is impact erosion (c). Impact erosion refers to the process by which the Moon's surface is continually bombarded by meteoroids and comets, resulting in the formation of craters and the gradual wear and tear of the lunar landscape.
What created the craters on the Moon? ›
These craters formed when rocks or comets from space smashed into the surface of the Moon. The impact was so powerful that it pulverized the ground – creating what we call regolith – and sprayed it out to form those ejecta rays. You can make craters like those on the Moon using simple baking ingredients!
What are the topographic features of the Moon? ›
The surface of the Moon has many features, including mountains and valleys, craters, and maria—wide flat areas that look like seas from a distance but are probably solidified molten rock.
What is Moon mapping? ›
If you've ever read your horoscope, cast your birth chart, or stared up at the stars set against a clear evening sky, you know that the moon holds a lot of power. 'Moon mapping' is a practice that allows you to directly access the moon's energy and use it as a guide for your life.
What is the name of the largest impact crater on the Moon? ›
South Pole–Aitken basin, the Moon
Our first crater is a big one: the biggest, deepest and oldest impact crater on the Moon. It is 2,500km diameter, 6.2 to 8.2km deep and formed roughly 4.2 billion years ago.
What is the impact origin of lunar craters? ›
Evidence collected during the Apollo Project and from uncrewed spacecraft of the same period proved conclusively that meteoric impact, or impact by asteroids for larger craters, was the origin of almost all lunar craters, and by implication, most craters on other bodies as well.
What causes impact craters? ›
An impact crater is formed when an object like an asteroid or meteorite crashes into the surface of a larger solid object like a planet or a moon. To form a true impact crater, this object needs to be traveling extremely fast—many thousands of miles per hour!
What is most affected by the Moon? ›
The Moon exerts a strong gravitational pull that causes the changing tides in our oceans and seas. This gravitational pull is at its strongest during the New Moon and Full Moon, so here we experience the highest and lowest tides.
The crust has a thickness of about 43 miles (70 kilometers) on the Moon's near-side hemisphere and 93 miles (150 kilometers) on the far-side. It is made of oxygen, silicon, magnesium, iron, calcium, and aluminum, with small amounts of titanium, uranium, thorium, potassium, and hydrogen.
What are the three main effects the Moon has on Earth? ›
The Moon affects life on Earth in three main ways
According to Tom, there are three main ways in which the Moon impacts on life: time, tides and light. 'For many animals, particularly birds, the Moon is essential to migration and navigation.
What caused the holes in the Moon? ›
The Moon's craters preserve billions of years of history. Scientists have learned about the conditions of our early solar system by studying the composition, size, and distribution of these holes in the Moon's surface, created long ago by collisions with asteroids.
What is the lunar crater? ›
a bowl-shaped depression formed by the impact of a meteorite or bomb.
Why are impact craters always round? ›
As in the case of a bomb explosion, the shape of the resulting crater is round: ejecta is thrown equally in all directions regardless of the direction from which the bomb may have arrived.
What is the topography of the earth? ›
The definition of topography is the shape, size, and arrangement of geographical features of the Earth's surface in a given location. Geographical features may include lakes, rivers, streams, hills, valleys, volcanos, canyons, cliffs, plains, and coastlines.
What is the meaning of lunar landscape? ›
the landscape of the moon. a rugged, barren landscape similar to that of the moon. a representation of the moon's landscape.
What is the lunar coordinate system? ›
The selenographic coordinate system is used to refer to locations on the surface of Earth's moon. Any position on the lunar surface can be referenced by specifying two numerical values, which are comparable to the latitude and longitude of Earth.
What are the two main kinds of lunar landscape? ›
The surface of the moon shows two distinctive types of terrain: lighter colored regions that are known as the lunar highlands, and darker regions that are known as maria. It turns out that the highlands are the oldest exposed regions on the surface of the moon, while the maria are large flows of low viscosity lava.
