Observations of the masers in the course of RadioAstron mission yielded detections of fringes for a number of sources in both water and hydroxyl maser transitions. Some sources display numerous ultra-compact details. This proves that implementation of the space VLBI technique for maser studies is possible technically and is not always prevented by the interstellar scattering, maser beaming and other effects related to formation, transfer and detection of the cosmic maser emission.

For the first time cosmic water maser emission was detected with projected baselines exceeding Earth Diameter. It was detected in a number of star forming regions in the Galaxy and megamaser galaxy NGC 4258. Fringes from the water maser sources were detected on baselines exceeding 5 Earth Diameters (>65,000 km). This means that the angular resolution better than 40 microarcsec was directly achieved in the cosmic maser observations. The sharpest “direct” linear resolution better than 4 million kilometers was achieved in observations of the maser in Orion. Modelling of the data on Cep A water maser indicates that the source contains features with the sizes smaller than that of the Sun. Difference in velocities of these features corresponds to velocity gradient exceeding highest known values by 1-1.5 orders of magnitude.

So, the major step from milli- to micro-arcsecond resolution in maser studies is done. Existence of the features with extremely small angular sizes is established. Further implementations of the space VLBI maser instrument for studies of the nature of cosmic objects, studies of interaction of extremely high radiation field with molecular material and studies of the matter on the line of sight are planned.