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EI2GYB > ASTRO 15.03.23 10:32l 147 Lines 7422 Bytes #999 (0) @ WW
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Subj: A brief history of the UK's Winchcombe meteorite
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A brief history of the UK's Winchcombe meteorite
In 2021, searchers recovered a meteorite that fell over the U.K. just hours
earlier. Scientists have now reconstructed its story.
By Martin D. Suttle, The Conversation | Published: Tuesday, March 14, 2023
On Feb. 28, 2021, for the first time in 30 years, a meteorite fell in the U.K.
and was later recovered by scientists. Today, there's an international effort
to study this space rock and learn more about its place in the early solar
system.
This meteorite is named after Winchcombe, the town in Gloucestershire where
several fragments were recovered - including a piece that landed on the
driveway of a family home.
The meteorite formed 4.5 billion years ago in the distant outer solar system,
beyond the orbit of Jupiter. We refer to such objects as primitive because they
contain some of the earliest solid material to form in our cosmic neighborhood,
offering insights into a time when our solar system was in its infancy.
Over time, much of this solid material merged to form larger objects, which
eventually led to the emergence of planets. Some of the early building blocks
that avoided being consumed in this process of planetary assembly are present
today as asteroids or even smaller objects. The Winchcombe meteorite is just
such a celestial body.
Some of these free-roaming planetary building blocks may have been responsible
for delivering water to the early Earth. Therefore, Winchcombe can provide a
glimpse into the activity of water on solid bodies in the ancient solar system.
Path through space
Winchcombe is a rare type of meteorite known as a CM chondrite. These
meteorites are characterised by high concentrations of water and organic matter
(molecules with chains of carbon atoms), both of which are essential
ingredients for the emergence of life.
We know the path through space that the Winchcombe object took - its orbit -
before it fell to Earth. It is one of only five primitive, water-bearing
chondrites for which scientists have this information. Knowing its orbit means
we can pinpoint where in the solar system it came from.
The pieces of this meteorite were recovered very rapidly - within 12 hours of
arriving on Earth. This means there was little time for water from Earth's
atmosphere to react with and contaminate the meteorite. Taken together with the
meteorite's rarity, primitive characteristics and distant origin, its swift
recovery makes the object an ideal candidate for studying the role of asteroids
in the early solar system.
The meteorite was probably once part of a larger asteroid. But looking at
pieces of the Winchcombe object under the microscope, it quickly became clear
that it is not one rock but many - a complex mix of fragments loosely held
together. This structure is the result of collisions between larger asteroids
in space.
The debris field created by the collision subsequently merged to form a new
population of smaller second-generation asteroids referred to as rubble-pile
objects because of their loose, blocky configuration. Winchcombe came from one
of these rubble-pile bodies - fragmented remains of the diverse rocky objects
that existed in the age before planets.
Space mud
Each rock fragment that makes up the Winchcombe meteorite records a distinct
history, revealing, for example, differences in the amount of water it
interacted with, and implying that the parent asteroid had a complex structure.
These observations point to either variable amounts of water on that parent
body, which condensed as ice as the asteroid grew, or the uneven flow of water
through the asteroid. When space rocks come into contact with liquid water they
begin to change, forming an unusual form of dark black, fine-grained "space
mud".
Researchers from across the world jump at the chance to study these minerals
because they hold, inside their crystal structure, molecules of the original
water that flowed on these asteroids.
A group of scientists accurately measured the different isotopes (or chemical
forms) of the hydrogen present in the Winchcombe meteorite. Along with oxygen,
hydrogen is one of the two chemical elements in water. The scientists' findings
demonstrated that water contained within the meteorite is very similar to the
water on Earth.
This strengthens a theory that asteroids played a critical role in delivering
water to the early Earth and thereby generating the oceans we see today.
Catastrophic collision
At some point, chemical reactions between water and rock were halted by the
catastrophic collision with another asteroid. This event shattered the
meteorite's parent body. Most of the rock fragments in the Winchcombe meteorite
are very small, less than 0.04 inches (1 millimeter) in size. This pattern of
small pieces is evidence of the high-energy collision but also the signature of
a weak asteroid.
As our understanding of planetary building blocks grows, we are increasingly
recognising that the types of planetary bodies represented by the Winchcombe
meteorite no longer exist in their original form.
Most, if not all, small asteroids (those measuring less than 6.2 miles [10
kilometers] in diameter) are likely to be rubble-pile bodies. Winchcombe is a
relic from that time and a testament to the fate of most asteroids. We can
summarie their history in a few simple words: hot and wet, then smashed to
rubble.
Studying Winchcombe has also helped us to understand how these types of
meteorites break-up in the atmosphere and, therefore, why they are rarely found
as large rocks.
Research on the Winchcombe meteorite continues and there are many more science
questions that we hope to answer. One particularly interesting study relates to
the type and amount of organic matter within Winchcombe and whether organic
matter delivered by meteorites played a role in the supply of nutrients - food,
essentially - for the emerging life on Earth.
More info and images at:
https://astronomy.com/news/2023/03/a-brief-history-of-the-winchcombe-meteorite
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