Discussion Overview
The discussion centers around whether an emission spectrum of Earth has been recorded from outer space by spacecraft. Participants explore the implications of such measurements for understanding Earth's atmospheric properties and compare this to the methods used for analyzing extrasolar planets.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- One participant inquires about the existence of an emission spectrum of Earth recorded from outer space, drawing a parallel to how extrasolar planets are analyzed.
- Another participant argues that recording such a spectrum may not be necessary for Earth, as we have more knowledge about its atmosphere from within, suggesting that measurements from orbit are more for mapping purposes.
- A different viewpoint mentions that there is a reflected component resembling the sun's emission spectrum and suggests that the average temperature of Earth could yield a blackbody spectrum centered in the infrared, though they are unsure of any measurements taken.
- One participant asserts that NASA has been conducting measurements related to Earth's emission spectrum since 1975, referencing the Earth Radiation Budget experiment on the Nimbus 6 satellite.
- Another participant notes that the EPOXI team is currently performing observations of Earth for exoplanet characterization, utilizing the Deep Impact spacecraft to gather time-resolved imaging in various wavebands, which may provide a low-resolution spectrum.
Areas of Agreement / Disagreement
Participants express differing views on the necessity and existence of an emission spectrum of Earth recorded from space. While some assert that such measurements have been made, others question their relevance or existence, indicating that the discussion remains unresolved.
Contextual Notes
There are limitations regarding the assumptions about the necessity of measuring Earth's spectrum from space, as well as the definitions of what constitutes an emission spectrum in this context. The discussion also reflects uncertainty about the completeness of existing data and measurements.