Investigations of cometary gas and dust using WISE/NEOWISE from Year 1 and Year 2 of the reactivating mission

The Wide-field Infrared Survey Explorer (WISE) mission was launched in 2009 to survey the entire sky in the mid-infrared (3.4, 4.6, 12, and 22 μm). By October 2010, the primary and secondary cryogen tanks were depleted, making the 12 and 22 μm channel inoperable while the mission continued to collect data until February 2011, when the spacecraft was placed into hibernation. The spacecraft was then reactivated in December 2013 (Mainzer et al. 2014), was re-named NEOWISE and has accumulated data using the two infrared wavelength bands (3.4 and 4.6 mm). After more than a decade searching for Near-Earth Objects (NEOs), the mission ended in August 2024.

 

WISE/NEOWISE primary goal was to discover and characterize Near-Earth Objects (Wright et al. 2010) but was also able to constraint dust and gas production rate. The dust signal is dominating the signal in the W1 band (3.4 μm) and can be used to constrain the gas signal in the W2 band (4.6 μm). One of the advantages of the NEOWISE data is that we can constrain CO and CO₂ (CO+CO₂) production in comets. Due to significant telluric contamination, CO₂ is detectable only from space (Bockelée-Morvan et al. 2004), owing to its self-absorption in Earth’s atmosphere. WISE/NEOWISE increased dramatically the amount of comet’s data to constrain gas and dust production rate when comets are showing activity.

 

We will investigate the building blocks of comets — cometary gas and dust components. We will use data from NEOWISE - Year 1 and Year 2 of the reactivated mission (2014 and 2015). We will focus on CO+CO₂, which are known to be the most abundant volatiles in comets after water. They are likely the main driver of the activity of comets at large heliocentric distances (R_h≥3 AU). Getting simultaneous gas and dust production in comets is very useful to derive the dust-to-gas ratio which is a fundamental parameter influencing cometary activity and constraining cometary origin. We will investigate the relationship between gas and dust production rates and the perihelion distance (q) of detected comets, along with their heliocentric distance (R_h) evolution.