We have surveyed all conventional methods proposed or conceivable for obtaining resolved images of an Earth-like exoplanet. Generating a $10\times 10\mathrm{pixel}$ map of a $1R_{\oplus }$ world at 10 pc demands $\approx 0.85\mu \mathrm{as}$ angular resolution and photon collection sufficient for $\mathrm{SNR}\gtrsim 5\mathrm{per}$ “micropixel.” We derived diffraction-limit and photon-budget requirements for (i) large single-aperture space telescopes with internal coronagraphs, (ii) external starshades, (iii) space-based interferometry (nulling and non-nulling), (iv) ground-based extremely large telescopes with extreme adaptive optics, (5) pupil-densified “hypertelescopes,” (vi) indirect reconstructions (rotational light-curve inversion, eclipse mapping, intensity interferometry), and (vii) diffraction-occultation by Solar System bodies. Even though these approaches serve their primary goals—exoplanet discovery and initial coarse characterization—each remains orders of magnitude away from delivering a spatially resolved image. In every case, technology readiness falls short, and fundamental barriers leave them 2–5 orders of magnitude below the angular resolution and photon-budget thresholds needed to map an Earth analog even on decadal timescales. Ultimately, an in situ platform delivered to $\lesssim 0.1\mathrm{AU}$ of the target could, in principle, overcome both diffraction and photon-starvation limits—but such a mission far exceeds current propulsion, autonomy, and communications capabilities. By contrast, the solar gravitational lens—providing on-axis gain of $\sim {10}^{10}$ and inherent $\mu \mathrm{as}\text{−}\mathrm{scale}$ focusing once an imaging spacecraft reaches heliocentric distances beyond $\gtrsim 550\mathrm{AU}$—appears uniquely capable of simultaneously meeting both the resolution and photon-budget requirements. If the several mission-specific risks (coronal calibration, focal-plane scanning, deconvolution) can be retired, the solar gravitational lens could enable true, resolved surface images and spatially resolved spectroscopy of Earth-like exoplanets in our stellar neighborhood.

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• Gravitational lenses
• Optical, UV, & IR astronomy