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In addition to stellar data, Gaia Data Release 2 (DR2) also contains accurateastrometry and photometry of about 14,000 asteroids covering 22 months ofobservations. We used Gaia asteroid photometry to reconstruct rotation periods,spin axis directions, and the coarse shapes of a subset of asteroids withenough observations. One of our aims was to test the reliability of the modelswith respect to the number of data points and to check the consistency of thesemodels with independent data. Another aim was to produce new asteroid models toenlarge the sample of asteroids with known spin and shape. We used thelightcurve inversion method to scan the period and pole parameter space tocreate final shape models that best reproduce the observed data. To search forthe sidereal rotation period, we also used a simpler model of a geometricallyscattering triaxial ellipsoid. By processing about 5400 asteroids with at leastten observations in DR2, we derived models for 173 asteroids, 129 of which arenew. Models of the remaining asteroids were already known from the inversion ofindependent data, and we used them for verification and error estimation. Wealso compared the formally best rotation periods based on Gaia data with thosederived from dense lightcurves. We show that a correct rotation period can bedetermined even when the number of observations $N$ is less than 20, but therate of false solutions is high. For $N > 30$, the solution of the inverseproblem is often successful and the parameters are likely to be correct in mostcases. These results are very promising because the final Gaia catalogue shouldcontain photometry for hundreds of thousands of asteroids, typically withseveral tens of data points per object, which should be sufficient for reliablespin reconstruction.

Reconstruction of asteroid spin states from Gaia DR2 photometry