Sky and Telescope - November 2015 - 10

News Notes

NASA / JPL-CALTECH / UCLA / MPS / DLR / IDA

MISSIONS I Dawn Reveals Ceres' Bright Spots, Haze

Mysterious white spots dot the ﬂoor of Occator, a crater on Ceres that's
92 km (57 miles) across. NASA's Dawn spacecraft has seen haze inside
the crater that appears to be linked to the spots.

New observations from NASA's Dawn orbiter (S&T: Apr. 2015,
p. 20) show bright spots, a pyramid-shaped mountain, and a
mysterious haze on the dwarf planet 1 Ceres.
Mission scientists ﬁ rst saw bright spots on the surface as
the spacecraft approached its destination. These spots veritably shine inside Occator, one of Ceres' large craters, and also
appear elsewhere on the surface. Dubbed faculae by Dawn principal investigator Christopher Russell (University of California,
Los Angeles), after the bright spots that appear in the Sun's
photosphere, they might be exposures of ice or salt. Dawn's
upcoming spectral measurements should settle the question.
"The lifetime of ice is quite short at the surface of Ceres, so if

it's ice it must have been very recently exposed or be constantly
replenished," says asteroid specialist Andrew Rivkin (Johns
Hopkins University Applied Physics Laboratory).
"Anything that bright and that small indicates to me transient behavior," conﬁrms Russell, who reviewed the mission's
ﬁndings on July 21st at the 2015 NASA Exploration Science
Forum in Moﬀett Field, California.
Dawn also detected what looks like a haze inside Occator, visible at noontime when observed at a glancing angle.
It doesn't extend or ﬂow over the crater's rim. If real, it's the
ﬁrst-ever haze observed on a body in the asteroid belt. Haze
suggests the presence of sublimating ice, which could point
toward geologic activity that is somehow dredging water ice up
from the dwarf planet's interior. A curious network of shallow
fractures, called catanae, also slices through the region. One of
them cuts directly through Occator and its central bright spot.
The surface of Ceres is peppered with impact craters,
though few are very large - Yalode, 271 km (168 miles) across,
tops the list. Most fall into three types: simple, central-peak,
and central-pit craters. Many show evidence of landslides and
ﬂow features, which again provide tantalizing hints of past geologic activity. This theory is further bolstered by observations
from ESA's Herschel space observatory, which in 2011-13 found
evidence for water vapor hovering over speciﬁc regions.
Ceres even has a lonely mountain, dubbed "The Pyramid"
for its strange, steep-sloped geometry. It measures 30 km
across at its base and 5 km high. Some sides are stained white.
"We don't understand it," admits Russell. The Dawn team is
still waiting on spectra of the surface to analyze the quasi-faceted peak, which will come in January 2016, when Dawn enters
its closest (and ﬁnal) orbit over Ceres.
■ EMILY POORE

SETI I "Breakthrough" Projects Push E.T. Search Forward
On July 20th, Russian internet investor Yuri Milner announced he's committing $100 million to an ambitious
SETI endeavor for the next 10 years. The
project, named Breakthrough Listen, is
a spinoﬀ of Milner's Breakthrough Prize
Foundation, which bestows awards for
innovative work in fundamental physics,
life sciences, and mathematics.
The Breakthrough Listen team will
use two radio-search strategies. The ﬁrst
is a targeted search, using the 100-meter
Green Bank telescope in West Virginia
and the Parkes 64-m antenna in Australia
10

November 2015 sky & telescope

to examine the nearest 1 million stars for
radio-emitting civilizations. The second is
a shallower, wide-sky sweep of the Milky
Way's center and midplane to encompass
more than 100 billion stars. The instruments will also take protracted stares at
100 of the nearest galaxies. One-third of
the funds will go toward developing powerful new receivers and processors.
The plans call for an optical SETI
search as well, using data from Lick's
2.4-m Automated Planet Finder telescope.
Also announced was $1 million for
Breakthrough Message, an open compe-

tition for ideas about what, if anything,
Earth should transmit if the team ﬁnds
another civilization. Breakthrough Initiatives says it will not dispatch any message
until a global debate has decided whether
calling extra attention to ourselves this
way is a good idea.
Read more about the projects and
watch a video of the press conference at
http://is.gd/leapseti.
■ ALAN MACROBERT

To get astronomy news as it breaks,
visit skypub.com/newsblog.

http://www.is.gd/leapseti http://www.skypub.com/newsblog

Sky and Telescope - November 2015

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