The latitudinal and seasonal variations of D/H and O2 on Mars

We propose to use HIFI to determine latitudinal and seasonal variations of HDO, H218O, O2 and CO on Mars. The water data will be used to retrieve the D/H ratio and study its variations with latitude and season. The martian D/H ratio, presently poorly known, is a an important parameter as its excess on Mars (about 5 times the terrestrial value) is interpreted as the signature of an early outgassing of the martian atmosphere. In addition, models predict a possible variation of D/H with latitude and season, as an effect of condensation processes and surface/atmosphere interactions. The O2 and CO data will be used to study the cycle of these two noncondensible species as a function of the solar longitude. Results will be compared with climate models which predict significant variations of all these species. Our data will provide important constraints to photochemical models. H2O is known to be maximum at high northern latitudes during northern summer, while CO and O2 are expected to be maximum at high southern latitudes at the same time. Some CO variations have been observed in the infrared but not in the millimeter/submillimeter range so far. No information is presently known about the possibile variations of O2. Herschel is unique in its capability to observe O2 and H2O.We propose to observe Mars in three positions (North, Center and South) at two different seasons, with Ls close to 50 deg. and 120 deg. respectively. We will use AOT II2 mode (raster scan with DBS) limited to 3 points. We have chosen highfrequency transitions to get the maximum spatial resolution. We propose to observe 3 settings: (1) H218O and HDO around 1630 GHz, (2) O2 and HDO around 1815 GHz and (3) 13CO and C18O around 1867 GHz. The total observing time is 26.3 hours. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]