A
more creditable conjecture is that the earth and Moon formed at the same time
and thus naturally shared the same chemistry.
This eliminates a lot of impossible impact scenarios and impossible
capture scenarios as well.
Recall
that planetary position is dictated by Jupiter which sets up available
geodesics that the planetary orbits converge to rather rapidly. Appropriate planets then set up housekeeping
and scour their own orbit as well.
Add
in my conjecture of Jupiter birthing planets because it is at a key point of
rotational instability as discovered by theorists forty years ago. Jupiter does the necessary gathering of
material and then is forced to calve a planet or even a planet and its moon(s).
What
makes this conjecture strangely viable it the special nature of Venus. The surface rock is barely below molten and
the planet continues to cool. A recent
genesis solves that and also explains the Red Spot on Jupiter at the same time.
It
may even turn out that all our planets were birthed by Jupiter, mostly during
the early stages in which the over spinning Jupiter threw out a massive rocky
planet as well as a less dense gas planet at the same time. Thus we have the separation of these two
types naturally explained.
If
a planet showed up and was sucked up by Jupiter as expected, we would have a
ring side seat of a planet(s) been born.
Moon's
Age Revealed, and a Lunar Mystery May Be Solved
Scientists have pinned
down the birth date of the moon to within 100 million years of the birth of the
solar system — the best timeline yet for the evolution of our planet's natural
satellite.
This new discovery about
the origin of the moon may help solve a mystery about why the moon and the Earth
appear virtually identical in makeup, investigators added.
Scientists have suggested
the moon was formed 4.5 billion years ago by a gigantic collision between a Mars-size
object named Theiaand Earth, a crash that would have largely melted the
Earth. This model suggested that more than 40 percent of the moon was
made up of debris from this impacting body. (Current theory suggests that Earth
experienced several giant impacts during its formation, with the moon-forming
impact being the last.)
However, researchers
suspected Theia was chemically different from Earth. In contrast, recent
studies revealed that the moon and Earth appear
very similar when it comes to versions of elements called isotopes — more so
than might be suggested by the current impact model. (Isotopes of an element
have differing numbers of neutrons from one another.)
"This means that at
the atomic level, the Earth and the moon are
identical,"study lead author
Seth Jacobson, a planetary scientist at the Côte d'Azur Observatory in Nice,
France, told Space.com. "This new information challenged the giant impact
theory for lunar formation."
How the moon evolved
No one seriously disputed
an impact as the most likely scenario for the formation of the moon, Jacobson said. However, a virtually atomically identical moon
and Earth threw the exact circumstances of the collision into question, he
said.
Now, by pinpointing when
the moon formed, Jacobson and his colleagues could help explain why the moon
and Earth are mysteriously similar. The scientists detailed their findings in
the April 3 issue of the journal Nature.
Efforts to date the
moon-forming impact have proposed a range of ages. Some have argued for an
early event, about 30 million years after the birth of the solar system,
whereas others suggested that it occurred more than 50 million years and
possibly as much as 100 million years after the solar system formed.
To help solve this
mystery, Jacobson and his colleagues simulated the growth of the solar system's rocky planets — Mercury, Venus, Earth and Mars — from a protoplanetary
disk of thousands of planetary building blocks orbiting the sun.
By analyzing how these
planets formed and grew from more than 250 computer simulations, the
researchers discovered that if the moon-forming impact was early, the amount of
material accreted onto Earth afterward was large. If the impact was late, the
amount would then be small.
Past research had
calculated the amount of material accreted onto Earth after the moon-forming
impact. These estimates are based on how on how so-called highly
siderophile or "iron-loving" elements such as iridium and
platinum show a strong tendency to move into Earth's core. After each giant
impact the nascent Earth sustained, these elements would have leached from
Earth's mantle and bonded with heavy, iron-rich material destined to sink to
Earth's heart.
Moon birth mystery
After the last giant impact that formed the moon, the mantle should have been almost completely stripped of iridium,
platinum and their cousins. These elements are still present in the mantle, but
only in small amounts, which suggests only a small amount of material accreted
onto Earth after the moon-forming impact.
The researchers
calculated the moon-forming impact must have occurred about 95 million years
after the formation of the solar system, give or take 32 million years.
"A late moon-forming
event, as suggested by our work, is very consistent with an identical Earth and
moon," Jacobson said.
In addition, recent
analyses propose that the impact that created the moon required a faster, more
energetic collision than previously suggested. This makes sense if the impact
took place relatively late with an older protoplanetary disk, as the new findings
suggest.
"Older disks tend to
be dynamically more active, since there are fewer bodies left in the disk to
distribute energy amongst," Jacobson said.
These new findings raise
an interesting new puzzle. While they suggest the moon and the Earth formed together
nearly 100 million years after the solar system arose, evidence from meteorites
from Mars suggests that the Red Planet formed as little as a few million years
after the solar system was born.
"This means that
Earth and Mars formed over dramatically different timescales, with Mars forming
much faster than the Earth," Jacobson said. "How can this be? Is it
just a matter of size? Location? What about Mercury and Venus? Did they grow on
similar timescales to the Earth or on timescales more similar to Mars? I think
these are some of the really important questions that we, as a community of
planetary scientists, will be addressing in the future."
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