Thursday, January 20, 2011

Moon has Liquid Core

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

One of the future challenges will be to establish a base on Mercury.  That has a night time surface temperature of 200K which is good enough to land.  A high temperature fabric over a base site could make it possible to operate during daytime which is quite long due to the slow rotation. The vacuum would act as the insulator. The real problem is protection from the massive radiation, not only on the ground but on the approach.

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

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

Moon has liquid core just like Earth... reveal sensors left on lunar surface 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-old technology that has yielded extraordinary results.

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

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

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

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

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

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

Uncovering details about the lunar core is critical for developing accurate 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 light elements - such as sulphur and oxygen - in a layer around our own core.

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

The Apollo Passive Seismic Experiment consisted of four seismometers deployed between 1969 and 1972, which recorded continuous lunar seismic activity until late 1977.

Dr Renee Weber, lead researcher a Nasa’s Marshall Space Flight Center in Huntsville, Alabama, said: 'We applied tried and true methodologies from terrestrial seismology to this legacy data set to present the first-ever direct detection 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 other seismic activity. 

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

Although sophisticated satellite imaging missions to the Moon made significant contributions to the study of its history and topography, the deep interior of Earth’s sole natural satellite remained a subject of speculation and conjecture since the Apollo era. 

Scientists had previously inferred the existence of a core, based on indirect estimates of the Moon’s interior properties, but many disagreed about its 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 the Moon’s fractionated crust.
To mitigate this challenge, Dr Weber and her team employed an approach called seismogram stacking, or the digital partitioning of signals.

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

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

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

The mission consists of twin spacecraft that will enter tandem orbits around the Moon for several months to measure the gravity field in unprecedented detail. 

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

1 comment:

LunaMoony said...

Although it is very speculative, nonetheless, the chemical conditions exist to suggest a feasible theory about terraforming the Moon, by using its own surface material, to be ignited with the intense heat of a small nuclear bomb. From materials brought by the Apollo astronauts, it shows that the Moon's surface contains an abundance of Oxygen, Hydrogen and Nitrogen, though these elements do not occur in free form on the Moon, but in rather strong chemical bounds in silicates of the regolith. (regolith = the layer of unconsolidated solid material, covering the bedrock of a planet). Read more here: