With support from a NASA Exobiology grant, Mojzsis has begun examining the effect of impacts on a new batch
of zircons found in areas that have been hit by more recent impacts.
Eventually, a stable rocky crust may have developed between Years 0.2 and 0.4 billion (see J. Bret Bennington's discussion of recycled zircons (crystals of zirconium silicate) from the rocks of western Australia in the Hadean Eon and the January 11, 2001 announcement
of zircons found north of Perth that appear to be 4.4 billion years old), covered and surrounded by soupy water that was already rich with organic compounds from interstellar space.
To help narrow the range of possible ages for the sandstone, Siddoway and Gehrels compared the age distributions of the Tava zircons with the age distributions
of zircons found in other sandstone formations in Colorado, Utah, northern Arizona, and southern California.
But a speck
of zircon found in the Australian outback is proving priceless to geologists.
Not exact matches
Tarduno's new results are based on the record
of magnetic field strength fixed within magnetite
found within
zircon crystals collected from the Jack Hills
of Western Australia.
Weiss» team
found that the rock conglomerate the
zircon crystals were in had been magnetized just 1 billion years ago, when it probably formed as part
of a volcanic eruption nearby.
They then applied a precise dating technique based on natural radioactive decay
of uranium, as Urs Schaltegger added: «In the sedimentary cross-sections, we
found layers
of volcanic ash containing the mineral
zircon which incorporates uranium.
One line
of evidence comes from hardy crystals called
zircons,
found primarily in granite — the formation
of granite requires subduction, the sinking
of a lithospheric slab into the mantle where it partially melts to produce so - called granitic magma.
For example, scientists have
found signs
of liquid water and even faint hints
of possible life in
zircon crystals dating back 4.1 billion years (SN: 11/28/15, p. 16).
Researchers led by Martina Menneken
of Westfälische Wilhelms - Universität in Germany
found that the diamonds are surrounded by
zircon crystals, which were dated between 3.1 billion and 4.3 billion years old.
Measurements on some 50 grains
of zircon from the gneiss rocks
found in Canada showed them to be 3.962 billion years old, with a margin
of error
of only three million years.
DUBLIN, Ireland - Scientist has
found the oldest form
of rock on Earth -
Zircon crystals.
«Ultimately, we
find that during intervals
of high
zircon production we have greenhouse conditions, and as
zircon production diminishes, we see a shift into our icehouse conditions.»
Armstrong, R., Vishnevysky, S., Koeberl., U-Pb analyses
of zircons from the Popigai imapct structure, Russia: first results, Meteorite Imapcts in
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