2000 miles wide gravitational anomaly under the Moon’s far side (June 2019)
This false-color graphic shows the
topography of the far side of the Moon. The warmer colors indicate high
topography and the bluer colors indicate low topography. The South Pole-Aitken
(SPA) basin is shown by the shades of blue. The dashed circle shows the
location of the mass anomaly under the basin. [NASA/Goddard Space Flight
Center/University of Arizona]
The GRAIL paired
spacecrafts are tuned to detect
gravitational anomalies, and were in operation most of 2012 to map the moon G
field ; they allowed us to discover a 2000 miles
wide gravitational anomaly under the Moon’s far
side, precisely buried several miles deep beneath the South
Pole-Aitken basin.
Baylor University’s
researchers just published their findings after a thorough study of the GRAIL/NASA
data – NASA’s Gravity Recovery and
Interior Laboratory (GRAIL) mission – in the journal Geophysical
Research Letters.
The two GRAIL spacecrafts are set
to fly one in front of the other to detect very small density fluctuations in
the Moon’s gravitational field. The leading spacecraft (called “Ebb”), when flying
over a region of higher gravitational density, will slightly accelerate just a
moment before the trailing spacecraft (“Flow”) will get to register that higher
density (and thus gets accelerated in its turn). In between those two events,
the distance between the two spacecrafts has been increased. Thus, by minutely measuring
the distance between the two GRAIL spacecrafts, scientists are able to map precisely
the gravitational field of the surface above which they fly.
Peter B. James, lead author of the Baylor University’s study,
compared the “unexpected mass” they found burried underground the basin to “a
pile of metal five times larger than the Big Island of Hawaii.”
Ian O’Neill, in his article on astroengine.com (ref. below) agrees with Peter James et al that this mysterious mass could bring us the key to the mystery of the moon formation 4 billion years ago. He ponders :
“How did all that material end up
buried inside the Moon’s mantle? The South Pole-Aitken basin was created four
billion years ago in the wake of a massive asteroid impact. In fact, the basin
is known to be one of the biggest impact craters in the solar system. If this
crater was formed by an impact, it stands to reason that the gravitational
anomaly is being caused by the dense metallic remains of the massive asteroid
that met its demise when the Earth-Moon system was in the throes of formation.”
In other words, “it’s likely the massive metallic corpse of an ancient asteroid.”
Peter James et al write: “One of the explanations of
this extra mass is that the metal from the asteroid that formed this crater is
still embedded in the Moon’s mantle.” Another explanation, according to the
authors, is that this burried mass could be an accumulation of “dense oxides
associated with the last stage of lunar magma ocean solidification.”
O’Neill
concludes : “It just so happens that we currently have a
mission at the basin, exploring this strange and unexplored place. On Jan. 3,
the Chinese Chang’e 3 mission achieved the first soft
touchdown on the lunar far side, landing inside Von Kármán crater and releasing a robotic rover,
Yutu-2, to explore the landscape. At time of writing, the mission is ongoing.”
Let’s
stay tuned on this exciting discovery and what it will unveil about our moon!
-------------------------------------------------------- Refs --------------------------------------------------------------
· There’s Something Massive Buried Under the Moon’s Far Side, by https://astroengine.com/2019/06/11/theres-something-massive-buried-under-the-moons-far-side/
· Peter B. James, et al. Deep Structure of the Lunar South Pole‐Aitken Basin. Geophysical Research Letter. First published: 05 April 2019. https://doi.org/10.1029/2019GL082252
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