Moon has Liquid Core

This is of great interest as itshould allow us to predict the minimal size for liquid based cores without relyingentirely on theoretical ideas.  It isclearly a fair bit smaller than the moon and must be expected everywhere.

One of the future challenges willbe to establish a base on Mercury.  Thathas a night time surface temperature of 200K which is good enough to land.  A high temperature fabric over a base sitecould make it possible to operate during daytime which is quite long due to theslow rotation. The vacuum would act as the insulator. The real problem isprotection from the massive radiation, not only on the ground but on theapproach.

The interesting thing is that therocks there are warm enough to h0old heat at 200K or thereabouts.  Thus mining into the surface may provide awell protected environment.

The same option should exist onthe moon. More importantly, a deep mine will access heat, which is naturallyavailable and could provide a thermal engine that can be used to produce waterand a range of raw material.  Such a minecould need to penetrate several miles before it becomes effective (two miles isgood enough on Earth for most needs except geothermal.

Moon has liquid core just like Earth... reveal sensors left on lunarsurface by astronauts 40 YEARS ago

Last updated at 1:16 PM on 7th January 2011

It's an unlikely marriage between state-of-the-art and 40-year-oldtechnology that has yielded extraordinary results.

Signals from seismic sensors left on the lunar surface by Apolloastronauts in 1971 have revealed that the Moon has a liquid core similar toEarth's.

Scientists at Nasa applied contemporary seismological techniques to thedata being emitted from sensors placed by their colleagues during the program's heyday.

Core knowledge: Nasa applied contemporary seismological techniques todata being emitted from sensors left on the Moon in 1971. Scientists now thinkthe Moon has a solid, iron-rich inner core and a fluid, primarily liquid-ironouter core

The new research suggests the Moon possesses a solid, iron-rich innercore with a radius of nearly 150 miles and a fluid, primarily liquid-iron outercore with a radius of roughly 205 miles. 

Where it differs from Earth is a partially molten boundary layer aroundthe core estimated to have a radius of nearly 300 miles.

The data sheds light on the evolution of a lunar dynamo - a naturalprocess by which our Moon may have generated and maintained its own strongmagnetic field.

Uncovering details about the lunar core is critical for developingaccurate models of the Moon’s formation. 

The core contains a small percentage of light elements such as sulphur,echoing new seismology research on Earth that suggests the presence of lightelements - such as sulphur and oxygen - in a layer around our own core.

The research, published in the online edition of journal Science, usedextensive data gathered during the Apollo-era Moon missions. 

The Apollo Passive Seismic Experiment consisted of four seismometers deployedbetween 1969 and 1972, which recorded continuous lunar seismic activity untillate 1977.

Dr Renee Weber, lead researcher a Nasa’s Marshall Space Flight Centerin Huntsville, Alabama, said: 'We applied tried and true methodologies fromterrestrial seismology to this legacy data set to present the first-ever directdetection of the Moon’s core.' 

The team also analysed Apollo lunar seismograms using array processing,techniques that identify and distinguish signal sources of moonquakes and otherseismic activity. 

The researchers identified how and where seismic waves passed throughor were reflected by elements of the Moon’s interior, signifying thecomposition and state of layer interfaces at varying depths.

Although sophisticated satellite imaging missions to the Moon madesignificant contributions to the study of its history and topography, the deepinterior of Earth’s sole natural satellite remained a subject of speculationand conjecture since the Apollo era. 

Scientists had previously inferred the existence of a core, based onindirect estimates of the Moon’s interior properties, but many disagreed aboutits radius, state and composition.

A primary limitation to past lunar seismic studies was the wash of'noise' caused by overlapping signals bouncing repeatedly off structures in theMoon’s fractionated crust.
To mitigate this challenge, Dr Weber and her team employed an approachcalled seismogram stacking, or the digital partitioning of signals.

Stacking improved the signal-to-noise ratio and enabled the researchersto more clearly track the path and behaviour of each unique signal as it passedthrough the lunar interior.

Dr Weber said: 'We hope to continue working with the Apollo seismicdata to further refine our estimates of core properties and characterise lunarsignals as clearly as possible to aid in the interpretation of data returnedfrom future missions.'

Future Nasa missions will help gather more detailed data. The GravityRecovery and Interior Laboratory - or GRAIL - is a Nasa Discovery-class missionset to launch this year. 

The mission consists of twin spacecraft that will enter tandem orbitsaround the Moon for several months to measure the gravity field inunprecedented detail. 

It will also answer long-standing questions about Earth’s moon andprovide scientists a better understanding of the satellite from crust to core,revealing subsurface structures and, indirectly, its thermal history.

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