【讨厌小伙伴:火星正在摧毁火卫一】

【讨厌小伙伴:火星正在摧毁火卫一】早在1970年,美国科学家们发现火卫一上有很多深深的沟槽,但是最近他们才发现,这些沟槽是由火星引力引起的,并且这一过程仍在不停地发生。科学家们表示,火卫一极有可能发生地貌变化和形体改变,我们可以通过其轨道改变和潮汐增减研究这一现象。

Mars is destroying its moon: Grooves on Phobos' surface hint that the red planet’s gravity is tearing it apart

By SARAH GRIFFITHS

Grooves on the surface of Mars’ largest moon suggest it is being destroyed by its parent planet.
While scientists have long suggested it is doomed to be destroyed, the ‘extensive system of grooves’ the first signs that the rocky satellite is gradually been torn apart.
They were first spotted in the 1970s, but new analysis shows the grooves match up with regions being put under stress.
Experts have predicted Phobos, perhaps aptly named after the character fear and panic in Greek mythology, will eventually be destroyed because it us so close to Mars that the planet’s tidal pull is shrinking its orbit.
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In millions of years, it is expected these forces will rip the moon apart before its pieces smash into Mars, New Scientist reported.
Experts first learned of the moon’s long, parallel grooves measuring 328 to 656 feet (100-200 metres) wide and 33 to 98 feet (10-30metres) long when the area was surveyed by the Mariner 9 and Viking orbiters in the 1970s.

They assumed they were cracks made by a large impact, or rows of debris on a homogenous lump of rock.
But in 2008, the Mars Express spacecraft revealed that Phobos is really a ball of rubbish stuck together by a thick layer of dust, meaning the grooves were unlikely to have been caused by a massive impact, which could have blown the rocky body apart.

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Terry Hurford, of Nasa’s Goddard Space Flight Centre in Greenbelt, Maryland, calculated the effect of stress tidal forces on Phobos using a computer model.
‘We calculate the surface stress field of the de-orbiting satellite and show that the first signs of tidal disruption are already present on its surface,’ his team write in the study.
‘Most of Phobos’ prominent grooves have an excellent correlation with computed stress orientations,’ it says, meaning that the marks are aligned with regions under the most stress.
Dr Hurford, who will present the results at a meeting of the Geological Society of America, said: ‘The grooves are the first sign of tearing it apart.’
There is a theory that the grooves may be faults, which could explain why some of them seem to cross each other’s paths.
The study says: Our model results applied to surface observations imply that Phobos has a rubble pile interior that is nearly strengthless.
It suggests the moon is held together by a flexible outer layer of dust.
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‘This outer layer behaves elastically and can experience significant tidal stress at levels able to drive tensile failure.
‘Fissures can develop as the global body deforms due to increasing tides related to orbital decay.’
The researchers write: ‘Phobos may have an active and evolving surface; an exciting target for further exploration.’
They believe their findings could help the study of another satellite in our solar system – Triton, which is one of Jupiter’s moons and one of the few known to be geologically active.
While the study may seem dramatic, Dr Hurford believes Phobos will survive for millions of years.
‘We have not looked how far we can go before it completely fails,’ he said.

 

http://www.dailymail.co.uk/sciencetech/article-3300605/Mars-destroying-moon-Grooves-Phobos-surface-hint-red-planet-s-gravity-tearing-apart.html


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