Global

Spectroscopy (TPF)

Spectral lines in planetary atmospheres of extrasolar planets

Oxygen: 1% of Earth atmosphere; other gases to be determined

Imaging interferometry needs technical development

Kasting

Macroscopic imaging systems (e.g., Galileo's Solid State Imager)

Morphology of macroscopic life and ecosystems

Less than ~10-m spatial resolution

Solar system objects only

Soffen

Morphological

Light microscopy

Structure; evidence for viability (motility, biofilms); noninvasive

0.2-µm spatial resolution

Morphology only; no chemistry

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Electron microscopy (environmental SEM [ESEM], SEM, EDX)

High-resolution morphology and chemical composition (ESEM is noninvasive)

1-10 nm, 0.2 keV, 1% relative abundance

Requires contamination-free microscopes

Barker and Banfield

Electron microscopy (TEM, SAED, EELS)

Structure, redox state, mineralogy; invasive

1 nm, 0.2 keV, 1% relative abundance

Invasive sample preparation

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X- ray microscopy

Electronic state of molecules

Nanometer resolution

Requires sectioning

Jacobsen

Fluorescence microscopy

Structure; detect very small entities, macromolecules (nucleic acids and proteins); identify organisms (¹⁶S and ¹⁸S rRNA) and possibly viability number of ribosomes; mRNA)

Can be used to enumerate viruses (30- 50 nm)

Better preparation methods needed with rock and soil samples; at present time need to dislodge organisms for FISH

Stahl, D. McKay, Jacobsen, Cady

CT scan- XAFS imaging

Internal structure; noninvasive

Millimeters to centimeters

Higher spatial resolution needed

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Mineralogical

SEM-EDX

Structure and abundance of elements

1-10 nm, 0.2 keV, 1% relative abundance

Reduce diameter of EDX beam (<200 nm)

Barker and Banfield, Kirschvink

Ion and electron microprobes

Chemical and isotopic composition

Single organic molecules

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D. McKay

Light microscopy, optical broadband spectroscopy

Chemical composition; noninvasive

0.2-µm spatial resolution

Limitations in spatial resolution

Jacobsen, Cady, D. McKay