An astrometric mass estimate for asteroid (223) Rosa

Context. Outer main belt asteroid (223) Rosa is a possible flyby target of opportunity for the European Space Agency (ESA) JUpiter ICy moons Explorer (JUICE) mission when it passes the asteroid belt on the way to Jupiter. The very low albedo and the featureless red spectra indicate a P-type asteroid in the Tholen taxonomy, though the yet known bulk density does not appear to match this classification. <BR /> Aims: The aim of this work is to derive new estimates for the mass and bulk density of (223) Rosa. <BR /> Methods: We derived the mass of Rosa by analyzing the gravitational deflection of small "test" asteroids that had a close encounter with Rosa in the past. To find such events suitable for the mass determination, we performed an encounter search with about 900 000 asteroids over the time span 1980-2030. <BR /> Results: Three encounters were identified from which two independent mass estimates for Rosa were derived: M = (5.32 ± 2.17) × 10<SUP>17</SUP> kg and M = (3.15 ± 1.14) × 10<SUP>17</SUP> kg, respectively. The weighted mean is M = (3.62 ± 1.25) × 10<SUP>17</SUP> kg. This yields to a bulk density of ρ = 1.2 ± 0.5 g cm<SUP>−3</SUP>, when adopting an effective diameter of D = 83 ± 8 km. This bulk density estimate is consistent with typical densities for Tholen taxonomy P-type asteroids.