12 Mar 2022. “RIDE AGAINST THE WAR IN UKRAINE” Joined this event today. Carried #Ukraine banner from San Jose, CA to San Francisco, CA City Hall. Salute to all those fighting for #Freedom.

TOMORROW! Sat, Feb 8, 11am PT Cupertino Library The Moon & Mars: Amazing Places for Humans to Soon Explore. @SETIInstitute @MarsInstitute @KeplerUni @NASAAmes @NSS

MOONS OF MARS: SMALL BODIES, BIG MYSTERIES Nice article in @newscientist by @nadiamdrake on #Phobos & #Deimos, the two known moons of #Mars, and the unknowns they still are. @SETIInstitute @MarsInstitute @KeplerUni @NASAAmes @NASA @NSS

MARS "SQUARE STRUCTURE" OK. I've been getting too many questions so had to look into it. Sure enough, it's not an alien ruin. It's not even square. Just interesting geology. Never underestimate the wonders of geology. @SETIInstitute @MarsInstitute @KeplerUni @NASAAmes @NASA @NSS

TONIGHT! (Tue, Feb 5) "Are We Alone In The Universe?" Los Altos Library @sccld, 7pmPT. @SETIInstitute

@VinnyChirayil The paper is neither conjecture nor a theoretical model. It's merely a classification of terrain based on combining results from three data sets.

@VinnyChirayil Whipple proposed decades ago that comets are mixes of ice(s) & dirt. Only comet nuclei in Oort Cloud might have stable exposures of ice. The ones that approach warmer parts of solar system will lose surface ice and accumulate lag deposits of dirt/rock. Nothing inconsistent there.

@VinnyChirayil None of this is a defense. Neutron spectrometry does indicate H2O, or hydrated minerals, depending on context. On Mars, both were detected by neutron spectrometry and verified by landed missions. The H2O was not exposed, but buried at shallow depth (Phoenix mission).

@VinnyChirayil Yes, re the caves, we are talking about microenvironments. But even in the polar regions, many if not most caves will be too warm. But some, for which indirect lighting is minimized, could be cold enough.

@VinnyChirayil Yes, of course, H2O is only an interpretation of H. That's why the units used are WEH (Water Equivalent Hydrogen). But given the polar concentration of the H, water ice is the most plausible interpretation and leading hypothesis to be tested.

@VinnyChirayil Evidence for ice is mainly from 1) neutrons 2) radar 3) LCROSS impact. Given temps, all point to shallow subsurface ice. Shadowcam not seeing exposed ice was not a surprise. What was hoped for were glacial/periglacial landforms. But shallow subsurface ice is not excluded at all.

@VinnyChirayil That said, the relationship between PSRs, H2O ice and surface & subsurface temperatures is more complicated than most realize. See:

@VinnyChirayil The slide does not predict H2O ice on the floor. It's the (low res) footprint from orbital neutron spectrometry indicating where H2O is likely present within the top meter of the regolith, not "on" the floor.

@VinnyChirayil I don't have any expectation for ice to be present on the Moon's surface, except possibly in some absolute PSRs, i.e., with minimal indirect lighting from say crater rims or pit walls.

@VinnyChirayil Vesta is not relevant here because we are talking about PSRs on the Moon. The subsurface temperatures you mention on Vesta do not pertain to PSRs.

@VinnyChirayil That's not how neutron spectrometry works. Neutron spectrometry detects hydrogen within the top 1 meter of the regolith, not just at the surface. Not seeing ice on the surface floor of a H-rich PSR (say Shackleton) does not mean that H2O is not present in the shallow subsurface.

@VinnyChirayil The surface temperature on the floor of Shackleton remains too warm because of indirect solar illumination from the crater's rim (which is why Shadowcam can even image the floor). On the floor of a cave, indirect lighting from pit walls can be low enough to allow H2O ice.

RT @Firefly_Space: T-5 days until Blue Ghost says goodbye to Earth! With the accuracy we achieved on our first two burns, we were able to s…

@hi43238 @sccld @SETIInstitute @MarsInstitute @NASAAmes @KeplerUni @nss Well, I don't think we are alone either. But until we know this for a fact, we just don't.