Space/Science — HabitableZone

Space/Science » in reply to active geyser vs passive spot

What are we seeing?
nick hoffman — (archived)

Your emission angle argument is correct - we don't have enough parallax to see the plume of a geyser laid out across the surface.

What we DO see, imho, is the stain of dust fallen back down onto the surface as the record of wind blowing the plume sideways when it is/was active. So we may be able to see the record of now-inactive plumes (explaining why we rarely or never see fuzzy gas clouds at the origin of the stains, unlike the dust devils which HAVE been captured in action*). In fact, the lack of such observations may suggest that the dust venting occurs prior to solar illumination, in the "pre-dawn" days or weeks before the long polar winter night ends.

Equally, we see the integration of all actual wind flows during the time the geyser was active. The stains that look so stunningly like arrays of giant cubes are caused by bi-directional winds. Whether these are morning and afternoon winds or are two different stable atmospheric states that occur over time is a matter for detailed atmospheric modelling.

* There's an observational bias here. The Mars Observer spacecraft is in a sun-stationary orbit at 14:00 local time, so it always flies overhead at 2 in the afternoon. As such, that's ideal for catching red-handed phenomena that depend on afternoon effect - i.e. the hot rising air in warmest part of the day [on Earth you get dust devils at similar times of day and convective storms of other sorts tend to occur in the afternoon, too].

Geysers may be a "morning" phenomenon, certainly in terms of the decay of the perpetual night of polar winter. Maybe even in terms of local time. If we fly overhead only at 2 pm, we'll never see active phenomena that occur in the morning, evening, or nighttime...

Log in or register to post.

The whole thread (86 posts)