2019 – Posted in: Daily News – Tags: epicenter, LRO, LROC, moonquakes, Seismometer

SHRINKING MOON GENERATING MOONQUAKES

For: Preliminary & Mains
Topic covers: Lunar Reconnaissance Orbiter (LRO)/ Camera (LROC), Findings of study, Objectives & importance

News Flash

The Moon is shrinking as its interior cools — getting over 50 metres skinnier through the last several hundred million years — and causing quakes on the lunar surface, according to an analysis of imagery captured by NASA’s Lunar Reconnaissance Orbiter.

How study carried out?

The researchers/ scientists analysed data from four seismometers placed on the Moon by the Apollo astronauts using an algorithm, or mathematical programme, developed to pinpoint quake locations detected by a sparse seismic network. The algorithm gave a better estimate of moonquake locations.

Astronauts placed the instruments on the lunar surface during the Apollo 11, 12, 14, 15, and 16 missions. The Apollo 11 seismometer operated only for three weeks, but the four remaining recorded 28 shallow moonquakes — the type expected to be produced by these faults — from 1969 to 1977.

Highlights of Study

The moon’s surface crust is brittle, so it breaks as the Moon shrinks, forming “thrust faults” where one section of crust is pushed up over a neighbouring part.
Our analysis gives the first evidence that these faults are still active and likely producing moonquakes. Some of these quakes can be fairly strong, around five on the Richter scale.
The moon continues to gradually cool and shrink.
Using the revised location estimates from the new algorithm, the team found that eight of the 28 shallow quakes were within 30 kilometres of faults visible in lunar images.
Other evidence that these faults are active comes from highly detailed images of the Moon by NASA’s Lunar Reconnaissance Orbiter (LRO) spacecraft.
The Lunar Reconnaissance Orbiter Camera (LROC) has imaged over 3,500 of the fault scarps.
Weathering from solar and space radiation gradually darkens material on the lunar surface, so brighter areas indicate regions that are freshly exposed to space, as expected if a recent moonquake sent material sliding down a cliff.

Seismometers are instruments that measure the shaking produced by quakes, recording the arrival time and strength of various quake waves to get a location estimate, called an epicentre.

The epicenter in seismology is the point on the Earth’s surface directly above a hypocenter or focus, the point where an earthquake or an underground explosion originates.

Lunar Reconnaissance Orbiter (LRO)

In June of 2009, NASA launched the Lunar Reconnaissance Orbiter, a robotic spacecraft, now orbiting the Moon at an altitude of 50-200 km. LRO’s primary objective is to make fundamental scientific discoveries about the Moon.

LRO is currently in the Extended Mission phase, focused on collecting the data needed to address key lunar science questions, including:

Chronology/Bombardment
Crustal Evolution
Regolith Evolution
Polar Volatiles

Lunar Reconnaissance Orbiter Camera (LROC)

In operation since 2009, the Lunar Reconnaissance Orbiter Camera (LROC) is a system of three cameras mounted on the Lunar Reconnaissance Orbiter (LRO) that capture high resolution photos of the lunar surface.

LROC was originally designed to achieve the following measurement objectives:

Find potential landing sites
Map regions of permanent shadow or illumination
Create high-resolution maps of polar massifs with permanent or near-permanent illumination
Observe regions from multiple angles to derive high-resolution topography
Improve maps of mineralogical components of the lunar crust
Create a global morphology base map
Characterize the regolith
Determine impact hazards

Source: The Hindu

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