Although few have actually been there, the face of the “Man in the Moon” – who
faithfully accompanies us through life – is very familiar. The synchronous
rotation of the Moon taking the same amount of time to spin around its own axis
as it does to revolve around Earth is what causes the Moon to “lock eyes” with
Earth, resulting in one of its hemispheres constantly facing us. But why is this
particular half of the Moon locked with Earth, or was it pure coincidence that
it didn’t “turn its back” on us? Through careful analysis and simulations, Prof.
Oded Aharonson of the Weizmann Institute of Science’s Center for Planetary
Science, together with Prof. Peter Goldreich of the California Institute of
Technology and Prof. Re’em Sari of the Hebrew University of Jerusalem, have
shown that it is not coincidence but the Moon’s geophysical properties that
determine its orientation. Their findings have recently been published in the
journal Icarus.
The near side of the Moon is low lying and covered by
craters filled with dense, dark volcanic material, the pattern of which to some
resembles the Man in the Moon.
In contrast, the far side is predominately
made up of “higher” mountainous regions.
“Intuitively, we might actually
have expected the far side to be facing us as the high mountains, as opposed to
the low craters, would have brought the Moon closer to Earth, putting the system
in a lower energy state,” says Aharonson. Nature usually prefers lower energy
states, so why isn’t this the case? The motion of the Moon is a bit like the
motion of toy train circling around a track, with two hills and two
valleys.
The hills and valleys represent the different energy levels of
the orientation of the geophysically asymmetric Moon. Because of friction, the
train continues to lose energy until it doesn’t have enough to climb over the
hill, thus settling into one of the valleys. Which valley it settles in is
governed not by the depth of valleys, but rather by the height of the hill it
most recently crossed.
Similarly for the Moon, its maxima energy (the
hills in our analogy) governs the ultimate state of the Moon, not its minima
energy (the valleys).
According to the scientists’ simulations, the
energy values calculated for the current geophysical characteristics of the Moon
favor locking it in the current orientation.
“In fact, by ‘designing’
different models of the Moon – moving its mass around, and altering various
other parameters that affect its gravitational properties – we are able to have
complete control over which ‘valley’ the Moon settles into,” says
Aharonson.
Some might argue that the Moon would have locked with Earth
very early in its existence, when its properties were much different to today’s
moon, and so these findings might not be relevant in explaining the actual
events. The scientists – and indeed some evidence – suggest that the other side
of the Moon could have been facing Earth at some point but was hit out of sync
and then later relocked into the current orientation, as described by the new
findings. The Weizmann scientist concludes: “For me, what is most interesting is
not seeing the Man in the Moon, but the elegance of how the system
works.”
Animal model for organ repair
A sophisticated national center for
genetically engineering the sea anemone Nematostella will be opened as part of
the Science and Technology Ministry’s program to develop scientific and
technological infrastructure in marine biology.
The remarkable ability of
this animal to regenerate its body parts could help further research into organ
repair in humans. The research will include Hebrew University of Jerusalem
developmental biologist Dr. Uri Gat, Bar-Ilan University coral researcher Dr.
Oren Levy and Dr. Tamar Lotan, a researcher of sea anemones and jellyfish at the
University of Haifa.
The Nematostella is a sea anemone belonging to a
large phylum of animals called Cnidarians that are among the most ancient
animals on the evolutionary ladder. These animals, which include sea anemones,
corals, jellyfish and hydra, have stinging cells on their tentacles through
which they can devour larger creatures and pose a nuisance and even a danger to
bathers.
To study a particular animal, researchers must find an animal
model that can easily be grown under laboratory conditions and studied in all
stages of its life cycle. To do this, scientists use small animals that grow and
multiply quickly and whose genetic code is known, such as fruit flies and mice.
Nematostella is the first animal among the cnidarians that can be used as an
animal model.
According to Gat, who is participating in establishing the
new center and the first to introduce the Nematostella animal model system into
Israel, although the Nematostella is a very simple, ancient life form, it is
rich in genes, many of which are in common with humans and which constitute
earlier versions of parallel genes in humans.
“Nematostella allows us for
the first time to find the ancestral genes to the important developmental
pathways that are common to all animals, and thus to understand their role in
the initial course of evolution, which may shed light on the function and
importance of these genes in humans,” says Gat. “For example, the Cnidarian
developed one of the first nervous systems in animals, so if we learn how it was
created and how it functions we could have new tools for researching and
understanding the nervous system in humans.”
Unlike humans, Nematostella
have the rare ability to restore large parts of the body that have been
damaged.
According to Gat, research into the creature will enable a
deeper understanding of injury repair processes that are similar to processes in
humans, thus contributing to the future development of new drugs that can speed
wound healing in humans and the development of new innovations for
rehabilitating damaged organs.
Lotan says the center will investigate the
active mechanism of the Nematostella’s stingers to discover ways to prevent
injuries from the sea anemone’s relative, the jellyfish.
Haifa
researchers are also examining the possibility of using it as a living sensor
that can alert humans to seawater contamination. The research center, the first
of its kind in the world, will be funded by the ministry and will be located at
Bar-Ilan University because of its central geographic location between the three
institutions.
Clarification
Contrary to a quote in last week’s Health Page article on “Microbe Hunter” Prof.
Nathan Citri, the Hadassah Women’s Zionist Organization of America’s Henrietta
Szold was not the founder of Youth Aliya. It was in fact the late Recha Freier,
who, working in Berlin in the face of the rise of Nazism, fought to get the
children out. Szold was one of those initially opposed to the idea of bringing
poor youngsters to Palestine because she thought the Yishuv could not afford it;
only at a later stage did she agree and ultimately help establish institutions
to absorb the children once they were here.