Science News - September 11, 2010

100 meters

estimated recent shrinkage of moon’s radius

1
kilometer

estimated recent shrinkage of Mercury’s radius

1–5 kilometers

possible shrinkage of moon’s radius since its formation

Shrinking moon
not so incredible
Widespread cliff formations
signal reduced lunar radius

By Gwyneth Dickey

The moon has shrunk in the past billion years, new high-resolution pictures suggest. Evidence comes in the form of cliffs all over the moon that have formed over the last million millennia like wrinkles on a dried-out piece of fruit.

Scientists have studied more than 70 of these cliffs, called lobate scarps, using Apollo mission images from the 1970s. The scarps are generally tens of kilome-

Cliffs called lobate scarps form as the
moon’s interior cools and shrinks.

650 m

ters long and less than 100 meters high. Researchers had hypothesized that the scarps resulted from shrinkage, but Apollo images did not show whether the scarps spanned the moon’s entire surface.

Now, images from NASA’s Lunar
Reconnaissance Orbiter reveal 14 new
scarps, providing the first definitive evi-
dence that the scarps occur globally.

Twinkle, twinkle, little fuzzy dot
Astronomers still wonder whether you’re a planet or not

By Ron Cowen

The faint celestial object TMR-1C has had a checkered past — and now it has a checkered present.

In 1998, NASA proclaimed that a picture taken the previous year of TMR- 1C — a fuzzy white dot — with the Hubble Space Telescope might go down in history as the first planet beyond the solar system to be photographed (SN: 6/6/98, p. 357). Susan Terebey, now at California State University, Los Angeles, led the discovery team, which suggested that the object’s location — at the end of a long, luminous filament emanating from two newborn stars — indicated that it was a planet cast off by those incipient suns.

Skeptical researchers noted that the apparent association between the object and the youthful stars might be a chance alignment. Only a year later, Terebey herself declared that the body was too hot to be a planet and could be just an old background star (SN: 6/26/99, p. 404).