AUTHOR=Iorio Lorenzo TITLE=Is the Recently Proposed Mars-Sized Perturber at 65–80 AU Ruled Out by the Cassini Ranging Data? JOURNAL=Frontiers in Astronomy and Space Sciences VOLUME=4 YEAR=2017 URL=https://www.frontiersin.org/journals/astronomy-and-space-sciences/articles/10.3389/fspas.2017.00028 DOI=10.3389/fspas.2017.00028 ISSN=2296-987X ABSTRACT=

Recently, the existence of a pointlike pertuber PX with 1 m_♂ ≲ m_X ≲ 2.4 m_⊕ (the symbol “♂” denotes Mars) supposedly moving at 65–80 AU along a moderately inclined orbit has been hypothesized in order to explain certain features of the midplane of the Kuiper Belt Objects (KBOs). We preliminarily selected two possible scenarios for such a PX, and numerically simulated its effect on the Earth-Saturn range ρ(t) by varying some of its orbital parameters over a certain time span; then, we compared our results with some existing actual range residuals. By assuming m_X = 1 m_♂ and a circular orbit, such a putative new member of our Solar System would nominally perturb ρ(t) by a few km over Δt = 12 year (2004 − 2016). However, the Cassini spacecraft accurately measured ρ(t) to the level of σ_ρ ≃ 100 m. Nonetheless, such a scenario should not be considered as necessarily ruled out since the Cassini data were reduced so far without explicitly modeling any PX. Indeed, a NASA JPL team recently demonstrated that an extra-signature as large as 4 km affecting the Kronian range would be almost completely absorbed in fitting incomplete dynamical models, i.e., without PX itself, to such simulated data, thus not showing up in the standard post-fit range residuals. Larger anomalous signatures would instead occur for m_X > 1 m_♂. Their nominal amplitude could be as large as 50 − 150 km for m_X = 2.4 m_⊕, thus making less plausible their existence.