Cidersomerset
17th March 2014, 23:09
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16 March 2014 Last updated at 18:36
Wrinkled Mercury's shrinking history
By Jonathan Amos
Science correspondent, BBC News
VMN7R4d5JX0
Mercury Mercury is 4,880km wide and is dominated by its giant iron core
The planet Mercury is about 7km smaller today than when its crust first solidified
over four billion years ago.The innermost world has shrunk as it has cooled over
time, its surface cracking and wrinkling in the process.Scientists first recognised the
phenomenon when the Mariner 10 probe whizzed by the planet in the mid-1970s.
But the latest images from the US space agency's Messenger satellite have enabled
researchers to refine their estimate for the amount of contraction.And, as they
report in the journal Nature Geoscience, it is significantly more than previously
realised.Mariner made two passes of Mercury, in 1974 and 1975, photographing
about 45% of the planet's surface.Evident in those pictures were long scars where
rock had been thrust upwards as the body shortened. These lobate scarps, as they
are known, typically run for hundreds of kilometres, and separate terrains that can
differ in height by thousands of metres.
qg5K94-0JNE
Mercury: The inner-most planet
Mercury eight colour map
Mercury was visited first by the Mariner 10 probe in the 1970s; and by Messenger http://news.bbcimg.co.uk/media/images/73559000/jpg/_73559348_mdis_global_enhancedcolor_caloris_orth_hd.jpgcurrently
The planet's diameter is 4,880km - about one-third the size of Earth
It is the second densest planet in Solar System; 5.3 times that of water
The Caloris Basin is the largest known feature (1,300km in diameter)
Scientists speculate there is water-ice in the planet's permanently shadowed craters
Mercury's huge iron core takes up more than 60% of the planet's mass
It is an extreme place: surface temperatures swing between 425C and -180C
Mercury is the only inner planet besides Earth with a global magnetic field
Messenger is the first spacecraft to go into orbit around the planet
From the Mariner evidence, researchers calculated Mercury must have decreased its
radius by about 1-3km over its history.But that figure was in conflict with modelling
studies that suggested a cooling object like Mercury should have contracted much
more in four billion years.Messenger helps to resolve the inconsistency. Since
entering into orbit in 2011, it has photographed 100% of the planet.This has
allowed for a more extensive study of the scarp features and the more subtle
wrinkled ridges that also criss-cross its surface.The new assessment now brings the
observed shrinkage - a reduction in radius of 7km - into the realm expected by the
models.Dr Paul Byrne from the Carnegie Institution in Washington DC is the lead
author on the Nature Geoscience paper. He marvelled at the surface features on planet.
"Some of these lobate scarps are enormous," he told BBC News.
"There's a structure called Enterprise Rupes in the southern hemisphere that is a
single scarp system. It's 1,000km long and in places has 3km of relief. Imagine
standing in front of it. It's Mercury's version of a mountain belt.
"It utterly dominates the topography and it is astounding given the diminutive size of Mercury."
The innermost world is a fascinating oddball. Whereas the Earth has an extensive
crust and mantle shrouding its metal core, Mercury is very different.Estimated to be
nearly 4,000km in diameter, the planet's metal core is its defining feature. It is
covered only by a thin rocky veneer that may be little more than 400km
thick.Although some of the core must still be liquid, part of it will have cooled and
solidified, losing volume as a result. This will have scrunched the thin, overlying
layer of rock. Europe and Japan plan to launch a joint mission to Mercury to follow
up Messenger's observationsThe BepiColombo venture should launch in 2016. One
of its principal investigators will be Dr Dave Rothery from the UK's Open University.
"People used to think the Earth was shrinking - which it is a little bit, but we can't
see it because of the way tectonic plates are created and destroyed on the Earth,"
he explained.
"Before we understood plate tectonics, people thought mountain belts on Earth
were because the planet was shrinking and forcing stuff upwards, and areas of
thick accumulation of sediment were where the crust was being forced down by
contraction. We now know that's broadly speaking wrong, but this is the process on
Mercury because it's a one plate planet."
This has relevance as scientists try to understand planets beyond our Solar System.
Many of these, too, may have just the single plate and exhibit very similar surface-
crumpling features to those seen on Mercury.
http://news.bbcimg.co.uk/media/images/73616000/jpg/_73616688_enterprise.jpg
Enterprise Rupes Mountain ranges: Mercury is covered with massive scarps where
the surface has shortened
http://www.bbc.co.uk/news/science-environment-26564521
======================================================
Why Planet Mercury Is Shrinking
D5wfpuR0RDI
Published on 17 Mar 2014
The planet Mercury, which measures at around 3000 miles in diameter, or less than one
18th the mass and volume of Earth, is slowly getting smaller. Researchers estimate that
it has decreased in size by over 4 miles since it first solidified more than 4 billion years
ago.The planet Mercury, which measures at around 3000 miles in diameter, or less than
one 18th the mass and volume of Earth, is slowly getting smaller. Researchers estimate
that it has decreased in size by over 4 miles since it first solidified more than 4 billion
years ago. Doctor Dave Rothery from the Open University in the United Kingdom who
worked on the study is quoted as saying: "People used to think the Earth was shrinking
- which it is a little bit, but we can't see it because of the way tectonic plates are
created and destroyed on the Earth."
But Mercury reportedly only has one tectonic plate, and the liquid core of the planet is
slowly cooling and turning into a solid. This process causes the planet to lose volume
and wrinkles the rocky surface, making it slightly smaller.
NASA sent spacecrafts to study Mercury starting in 1974, but less than half of the planet
was documented at that time, and another mission didn't visit there for over 30 years.
The Messenger satellite began its orbit of Mercury in 2011 and has now taken pictures
of the entire planet's surface and collected data from rocks for analysis.
16 March 2014 Last updated at 18:36
Wrinkled Mercury's shrinking history
By Jonathan Amos
Science correspondent, BBC News
VMN7R4d5JX0
Mercury Mercury is 4,880km wide and is dominated by its giant iron core
The planet Mercury is about 7km smaller today than when its crust first solidified
over four billion years ago.The innermost world has shrunk as it has cooled over
time, its surface cracking and wrinkling in the process.Scientists first recognised the
phenomenon when the Mariner 10 probe whizzed by the planet in the mid-1970s.
But the latest images from the US space agency's Messenger satellite have enabled
researchers to refine their estimate for the amount of contraction.And, as they
report in the journal Nature Geoscience, it is significantly more than previously
realised.Mariner made two passes of Mercury, in 1974 and 1975, photographing
about 45% of the planet's surface.Evident in those pictures were long scars where
rock had been thrust upwards as the body shortened. These lobate scarps, as they
are known, typically run for hundreds of kilometres, and separate terrains that can
differ in height by thousands of metres.
qg5K94-0JNE
Mercury: The inner-most planet
Mercury eight colour map
Mercury was visited first by the Mariner 10 probe in the 1970s; and by Messenger http://news.bbcimg.co.uk/media/images/73559000/jpg/_73559348_mdis_global_enhancedcolor_caloris_orth_hd.jpgcurrently
The planet's diameter is 4,880km - about one-third the size of Earth
It is the second densest planet in Solar System; 5.3 times that of water
The Caloris Basin is the largest known feature (1,300km in diameter)
Scientists speculate there is water-ice in the planet's permanently shadowed craters
Mercury's huge iron core takes up more than 60% of the planet's mass
It is an extreme place: surface temperatures swing between 425C and -180C
Mercury is the only inner planet besides Earth with a global magnetic field
Messenger is the first spacecraft to go into orbit around the planet
From the Mariner evidence, researchers calculated Mercury must have decreased its
radius by about 1-3km over its history.But that figure was in conflict with modelling
studies that suggested a cooling object like Mercury should have contracted much
more in four billion years.Messenger helps to resolve the inconsistency. Since
entering into orbit in 2011, it has photographed 100% of the planet.This has
allowed for a more extensive study of the scarp features and the more subtle
wrinkled ridges that also criss-cross its surface.The new assessment now brings the
observed shrinkage - a reduction in radius of 7km - into the realm expected by the
models.Dr Paul Byrne from the Carnegie Institution in Washington DC is the lead
author on the Nature Geoscience paper. He marvelled at the surface features on planet.
"Some of these lobate scarps are enormous," he told BBC News.
"There's a structure called Enterprise Rupes in the southern hemisphere that is a
single scarp system. It's 1,000km long and in places has 3km of relief. Imagine
standing in front of it. It's Mercury's version of a mountain belt.
"It utterly dominates the topography and it is astounding given the diminutive size of Mercury."
The innermost world is a fascinating oddball. Whereas the Earth has an extensive
crust and mantle shrouding its metal core, Mercury is very different.Estimated to be
nearly 4,000km in diameter, the planet's metal core is its defining feature. It is
covered only by a thin rocky veneer that may be little more than 400km
thick.Although some of the core must still be liquid, part of it will have cooled and
solidified, losing volume as a result. This will have scrunched the thin, overlying
layer of rock. Europe and Japan plan to launch a joint mission to Mercury to follow
up Messenger's observationsThe BepiColombo venture should launch in 2016. One
of its principal investigators will be Dr Dave Rothery from the UK's Open University.
"People used to think the Earth was shrinking - which it is a little bit, but we can't
see it because of the way tectonic plates are created and destroyed on the Earth,"
he explained.
"Before we understood plate tectonics, people thought mountain belts on Earth
were because the planet was shrinking and forcing stuff upwards, and areas of
thick accumulation of sediment were where the crust was being forced down by
contraction. We now know that's broadly speaking wrong, but this is the process on
Mercury because it's a one plate planet."
This has relevance as scientists try to understand planets beyond our Solar System.
Many of these, too, may have just the single plate and exhibit very similar surface-
crumpling features to those seen on Mercury.
http://news.bbcimg.co.uk/media/images/73616000/jpg/_73616688_enterprise.jpg
Enterprise Rupes Mountain ranges: Mercury is covered with massive scarps where
the surface has shortened
http://www.bbc.co.uk/news/science-environment-26564521
======================================================
Why Planet Mercury Is Shrinking
D5wfpuR0RDI
Published on 17 Mar 2014
The planet Mercury, which measures at around 3000 miles in diameter, or less than one
18th the mass and volume of Earth, is slowly getting smaller. Researchers estimate that
it has decreased in size by over 4 miles since it first solidified more than 4 billion years
ago.The planet Mercury, which measures at around 3000 miles in diameter, or less than
one 18th the mass and volume of Earth, is slowly getting smaller. Researchers estimate
that it has decreased in size by over 4 miles since it first solidified more than 4 billion
years ago. Doctor Dave Rothery from the Open University in the United Kingdom who
worked on the study is quoted as saying: "People used to think the Earth was shrinking
- which it is a little bit, but we can't see it because of the way tectonic plates are
created and destroyed on the Earth."
But Mercury reportedly only has one tectonic plate, and the liquid core of the planet is
slowly cooling and turning into a solid. This process causes the planet to lose volume
and wrinkles the rocky surface, making it slightly smaller.
NASA sent spacecrafts to study Mercury starting in 1974, but less than half of the planet
was documented at that time, and another mission didn't visit there for over 30 years.
The Messenger satellite began its orbit of Mercury in 2011 and has now taken pictures
of the entire planet's surface and collected data from rocks for analysis.