Bibcode
DOI
Montañés-Rodriguez, P.; Pallé, E.; Goode, P. R.; Hickey, J.; Koonin, S. E.
Bibliographical reference
The Astrophysical Journal, Volume 629, Issue 2, pp. 1175-1182.
Advertised on:
8
2005
Journal
Citations
47
Refereed citations
34
Description
We report spectroscopic observations of the earthshine reflected from
the Moon. By applying our well-developed photometry methodology to
spectroscopy, we are able to precisely determine the Earth's reflectance
and its variation as a function of wavelength through a single night as
the Earth rotates. These data imply that planned regular monitoring of
earthshine spectra will yield valuable new inputs for climate models,
which would be complementary to those from the more standard broadband
measurements of satellite platforms. For our single night of reported
observations, we find that Earth's albedo decreases sharply with
wavelength from 500 to 600 nm, while being almost flat from 600 to 900
nm. The mean spectroscopic albedo over the visible is consistent with
simultaneous broadband photometric measurements. Unlike previous
reports, we find no evidence for either an appreciable ``red'' or
``vegetation'' edge in the Earth's spectral albedo, or for changes in
this spectral region (700-740 nm) over the 40° of Earth's rotation
covered by our observations. Whether or not the absence of a vegetation
signature in disk-integrated observations of the Earth is a common
feature awaits the analysis of more earthshine data and simultaneous
satellite cloud maps at several seasons. If our result is confirmed, it
would limit efforts to use the red edge as a probe for Earth-like
extrasolar planets. Water vapor and molecular oxygen signals in the
visible earthshine, and carbon dioxide and methane in the near-infrared,
are more likely to be powerful probes.