NASA: There’s enough ice on Mercury to encase Washington, D.C.
New evidence suggests Mercury's north polar region contains large deposits of ice. (NASA/Johns Hopkins Univers …NASA's Messenger spacecraft has discovered evidence that the planet Mercury has enough ice on its surface to encase Washington, D.C., in a block two and a half miles deep.
"For more than 20 years the jury
has been deliberating on whether the planet closest to the Sun hosts
abundant water ice in its permanently shadowed polar regions," writes
Sean Solomon of the Columbia University's Lamont-Doherty Earth
Observatory, the principal investigator of the Messenger mission. The
spacecraft "has now supplied a unanimous affirmative verdict."
"These reflectance anomalies are
concentrated on poleward-facing slopes and are spatially collocated with
areas of high radar backscatter postulated to be the result of
near-surface water ice," Gregory Neumann of NASA's Goddard Space Flight
Center writes in the paper. "Correlation of observed reflectance with
modeled temperatures indicates that the optically bright regions are
consistent with surface water ice."
The study results were published on Wednesday in Science
magazine, which explains in its summary, "The buried layer must be
nearly pure water ice. The upper layer contains less than 25 wt.%
water-equivalent hydrogen. The total mass of water at Mercury's poles is
inferred to be 2 × 1016 to 1018 g and is consistent with delivery by comets or volatile-rich asteroids."
Radar imaging of Mercury has long suggested that there could be large deposits on the planet's surface, with reports dating to 1991. But today's report presents harder evidence supporting that theory.
Messenger has fired more than 10
million laser imaging pulses at Mercury's surface since arriving in its
orbit in 2011. Feedback from those pulses have helped NASA in its quest
to verify whether ice is present in Mercury's poles, which are largely
shielded from exposure to the sun's rays.
No comments:
Post a Comment