Hola amigos: A VUELO DE UN QUINDE EL BLOG., Gravedad de la Tierra ha influido en la orientación de miles de fallas que se forman en la superficie lunar como la luna se encoge, de acuerdo con los nuevos resultados de NASA's Lunar Reconnaissance Orbiter (LRO)
spacecraft.
More information...............
Earth's gravity has influenced the orientation of thousands
of faults that form in the lunar surface as the moon shrinks, according
to new results from NASA's Lunar Reconnaissance Orbiter (LRO)
spacecraft.
The gravitational forces the Moon and Sun exert are
responsible for Earth’s rising and falling tides. Earth’s gravity also
exerts forces on the Moon in the form of solid body tides that distort
its shape. The Moon is slowly receding away from Earth and forces build
as the Moon’s tidal distortion diminishes with distance and its rotation
period slows with time. These tidal forces combined with the shrinking
of the Moon from cooling of its interior have influenced the pattern of
orientations in the network of young fault scarps.
Credits: NASA/LRO/Arizona State University/Smithsonian Institution
Thousands of young, lobate thrust fault scarps have
been revealed in Reconnaissance Orbiter Camera images (LROC). Lobate
scarps like the one shown here are like stair-steps in the landscape
formed when crustal materials are pushed together, break and are thrust
upward along a fault forming a cliff. Cooling of the still hot lunar
interior is causing the Moon to shrink, but the pattern of orientations
of the scarps indicate that tidal forces are contributing to the
formation of the young faults.
Credits: NASA/LRO/Arizona State University/Smithsonian Institution
The map shows the locations of over 3,200 lobate
thrust fault scarps (red lines) on the Moon. The black double arrows
show the average orientations of the lobate scarps sampled in areas with
dimensions of 40° longitude by 20° latitude and scaled by the total
length of the fault scarps in the sampled areas. The pattern of the
black double arrows (orientation vectors) indicates that the fault
scarps do not have random orientations as would be expected if the
forces that formed them were from global contraction alone. Mare basalt
units are shown in tan.
Credits: NASA/LRO/Arizona State University/Smithsonian Institution
A prominent lobate fault scarp in the Vitello
Cluster is one of thousands discovered in Lunar Reconnaissance Orbiter
Camera images (LROC). Topography derived from the LROC Narrow Angle
Camera (NAC) stereo images shows a degraded crater has been uplift as
the fault scarp has formed (blues are lower elevations and reds are
higher elevations). Boulders in the crater have aligned in rows that
parallel the orientation of the fault scarp.
Credits: NASA/LRO/Arizona State University/Smithsonian Institution
A nadir (top) and perspective view (bottom) of a
prominent lobate fault scarp in the Vitello Cluster, one of thousands
discovered in Lunar Reconnaissance Orbiter Camera images (LROC). In the
perspective view, the Narrow Angle Camera (NAC) image is draped over
topography derived from NAC stereo images. A degraded crater has been
uplift as the fault scarp has formed. Boulders in the crater have
aligned in rows that parallel the orientation of the fault scarp.
Credits: NASA/LRO/Arizona State University/Smithsonian Institution
In August, 2010, researchers using images from LRO's Narrow Angle
Camera (NAC) reported the discovery of 14 cliffs known as "lobate
scarps" on the moon's surface, in addition to about 70 previously known
from the limited high-resolution Apollo Panoramic Camera photographs.
Due largely to their random distribution across the surface, the science
team concluded that the moon is shrinking.
These small faults are typically less than 6.2 miles (10 kilometers)
long and only tens of yards or meters high. They are most likely formed
by global contraction resulting from cooling of the moon's still hot
interior. As the interior cools and portions of the liquid outer core
solidify, the volume decreases; thus the moon shrinks and the solid
crust buckles.
Now, after more than six years in orbit, the Lunar Reconnaissance
Orbiter Camera (LROC) has imaged nearly three-fourths of the lunar
surface at high resolution, allowing the discovery of over 3,000 more of
these features. These globally distributed faults have emerged as the
most common tectonic landform on the moon. An analysis of the
orientations of these small scarps yielded a surprising result: the
faults created as the moon shrinks are being influenced by an unexpected
source—gravitational tidal forces from Earth.
Global contraction alone should generate an array of thrust faults
with no particular pattern in the orientations of the faults, because
the contracting forces have equal magnitude in all directions. "This is
not what we found," says Smithsonian senior scientist Thomas Watters of
the National Air and Space Museum in Washington. "There is a pattern in
the orientations of the thousands of faults and it suggests something
else is influencing their formation, something that's also acting on a
global scale -- 'massaging' and realigning them." Watters is lead author
of the paper describing this research published in the October issue of
the journal Geology.
The other forces acting on the moon come not from its interior, but
from Earth. These are tidal forces. When the tidal forces are
superimposed on the global contraction, the combined stresses should
cause predictable orientations of the fault scarps from region to
region. "The agreement between the mapped fault orientations and the
fault orientations predicted by the modeled tidal and contractional
forces is pretty striking," says Watters.
"The discovery of so many previously undetected tectonic features as
our LROC high-resolution image coverage continues to grow is truly
remarkable," said Mark Robinson of Arizona State University, coauthor
and LROC principal investigator. "Early on in the mission we suspected
that tidal forces played a role in the formation of tectonic features,
but we did not have enough coverage to make any conclusive statements.
Now that we have NAC images with appropriate lighting for more than half
of the moon, structural patterns are starting to come into focus."
The fault scarps are very young – so young that they are likely still
actively forming today. The team's modeling shows that the peak
stresses are reached when the moon is farthest from Earth in its orbit
(at apogee). If the faults are still active, the occurrence of shallow
moonquakes related to slip events on the faults may be most frequent
when the moon is at apogee. This hypothesis can be tested with a
long-lived lunar seismic network.
"With LRO we've been able to study the moon globally in detail not
yet possible with any other body in the solar system beyond Earth, and
the LRO data set enables us to tease out subtle but important processes
that would otherwise remain hidden," said John Keller, LRO Project
Scientist at NASA's Goddard Space Flight Center, Greenbelt, Maryland.
Launched on June 18, 2009, LRO has collected a treasure trove of data
with its seven powerful instruments, making an invaluable contribution
to our knowledge about the moon. LRO is managed by NASA's Goddard Space
Flight Center in Greenbelt, Maryland, under the Discovery Program,
managed by NASA's Marshall Space Flight Center in Huntsville for the
Science Mission Directorate at NASA Headquarters in Washington, DC.
Nancy Neal-Jones / William Steigerwald
NASA Goddard Space Flight Center, Greenbelt, Maryland
301-286-0039 / 6-5017
nancy.n.jones@nasa.gov / william.a.steigerwald@nasa.gov
NASA Goddard Space Flight Center, Greenbelt, Maryland
301-286-0039 / 6-5017
nancy.n.jones@nasa.gov / william.a.steigerwald@nasa.gov
Last Updated: Sep. 15, 2015
Editor: Karl Hille
Tags: Goddard Space Flight Center, LRO (Lunar Reconnaissance Orbiter), Moons, Solar System
NASA
Guillermo Gonzalo Sánchez Achutegui
ayabaca@gmail.com
ayabaca@hotmail.com
ayabaca@yahoo.com
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