Characterizing Habitable Worlds...

From the Moon

Margaret Turnbull - STScI / Carnegie

First: An astrobiologist appreciates the cosmic

significance of this meeting. What will they do?

A Few Take-home Lessons:The moon is fine for astronomy,

but not necessarily better than space.

Challenges are present (dust, radiation, thermal fluctuations) but surmountable.

If we go to the moon, it will NOT be so that we can do astrophysics.

A Few Take-home Lessons:Whether and how we conduct

astrophysics on the moon will depend on events which we can

inform but not control or predict.

Now is the time to identify sexy, simple astrophysics that can be carried out from

the moon in the “near” term.

FOR EXAMPLE...

Characterizing Habitable Worlds Around Nearby Stars

How common are they?

How old are they?

Where are they?

Are they inhabited?

Can we go there?

TPF-I

TPF-C

The Terrestrial Planet Finder The technology driver is the need to suppress starlight by a factor of 1 million (at mid-IR wavelengths) or 10 billion (at optical wavelengths) at milliarcsec from the star...probably needs to be a space mission, not lunar-based.

40 milliarcsec IWA10-10 starlight suppression atoptical wavelengths0.5-1.05 um

3-4m x 3-46.5-17 um10-6 starlight suppression

But Before TPF can happen, We have to understand:-what does a habitable planet look like?

-how can we probe its surface, atmosphere, and life forms?

=> and TPF precursor science begins at home...

TPF-I

TPF-C

The Terrestrial Planet Finder

3-4m x 3-46.5-17 um10-6 starlight suppression

What does our planet look like from (deep-ish) space?

Sagan et al. 1993 (Nature 365, 715): Galileo detects abundant oxygen, methane, and spatially variable “red edge” pigments at optical and near-IR wavelengths

What does our planet look like from space?

Woolf et al. (2002) and Turnbull et al. (2006): Earthshine

=> Spatially unresolved signal (like exoplanet observations).

What does our planet look like from space?

Terrile et al. 2007: Degeneracies!!

What does our planet look like from space?

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are needed to see this picture.

Change over time may be the key to

spatially characterizing planets

via spatially unresolved signals

What does our planet look like from space?

Photometric changes ~ 30%(Ford, Seager &

Turner 2003)

What does our planet look like from space?

Red edge variations ~30%

(Tinetti et al 2006)

(no clouds)

What does our planet look like from space?

Thermal variations ~50%

(Hearty et al 2007)

(AIRS data)

What does our planet look like from space?

Polarization variations 10%-40%

(Stam et al 2004)

=> Starlight is NOT polarized

What does our planet look like from space?

Polarization variations 10%-40%

(Stam et al 2004)

=> Starlight is NOT polarized

A Concept for TPF Prep Science from the Moon

PI: Margaret Turnbull, STScISee also:Traub et al.

“REFLECT” poster

(STScI’s NASA “LSSO” Proposal)

The ALIVE Idea:

Characterize Terrestrial Change.Do photometry, spectroscopy, and polarimetry of the Earth on an hourly basis for as long as possible in optical and near-IR wavelengths (possibly UV and thermal IR as well).

-Small telescope, Astronaut deployable

-Autonomously functioning after that

-Study change due to rotation, phases, seasons...solar cycles??

What does our planet look like from space?

ALIVE baseline

Extended Concept

The ALIVE Idea:

Use spatially resolved measurements in conjunction with models to find out:

To what extent can we characterize unknown worlds, given a spatially

unresolved signal?

The ALIVE Instrument Concept

ALIVE and Earth Science

The modern environmental movement was born of the Apollo missions.

ALIVE and Earth ScienceDuring “Full Earth”,what we lose in relevance to exoplanetswe gain in relevance to geoclimatology.

=> Triana-like science!

ALIVE and Earth Science“Hot spot” observations-spectral separation b/wground + plants enhanced-probe canopy structure as the earth turns-vegetation abundance and health

ALIVE and Earth ScienceLimb-to-limb cloudcover,albedo, and optical depth =>derive microphysics of clouds =>needed to constrain Earth’s albedo and thermal emission, critical for climate models

ALIVE and Earth Science

Obtain time- and space-resolved column measurements forgreenhouse gases produced by naturaland anthropogenic sources (CO2, CO, CH4)

ALIVE and Earth ScienceExtension into the UV:Cloud transmittance andabsorption,surface UV radiation,time- and space-resolvedmeasurements of ozone,aerosols, NO2

=> also critical to understanding Earth’s energy balance

PI: Margaret Turnbull, STScI

Cost/benefit trades to be investigated:-wavelength resolution reqs (R~250)-wavelength range (UV? thermal?)-spatial res reqs (~10km/100km)-power (RTGs? solar? batteries?)-location of deployment (poles?)-thermal control, dust mitigation-operations during lunar night?

PI: Margaret Turnbull, STScI