RE: Paleoastronomy and the K-T event

["Thomas R. Holtz, Jr." <tholtz@umd.edu>]

>From dinosaurtom2015@seznam.cz

>I'm new to the list and it's an honor for me to be finally a part of DML. I'
m interested in dinosaurs and astronomy as well and I'm curious about few
things. If anyone can help with this, I would be grateful. My questions
follow:

>1.) Is it possible to determine what daytime the Chicxulub impactor striked
the Earth? Was it day or night, what phase of the Moon then was etc.? Can
sediments, rhytmites or something else hold this information?

This one is easy: no. We have no clue at this moment. And it is
extraordinarily unlikely to be preserved (if nothing else, rhythmites
being deposited at the time would have likely been obliterated!)

 >2.) How long exactly was theday at theend of the Maastrichtian 66.0 Ma ago?
I found a study with a value of 23 hours 36 minutes, which is about 21
minutes shorter than today. Haw could that affect dinosaur biorhytms?

Good question. If you can find that study and post the source, we can
evaluate the research. As far as "biorhythms": how do you mean? Of course
they day/night cycle of the Maastrichtian would be the ones Maastrichtian
dinosaurs used.

>3.) When Chicxulub collided with Earth, how long did it take the pressure
wave to reach Hell Creek ecosystems located a few thousand kilometers to the
north? Is it possible that at least some dinosaurs survived the first wave?

You need a physicist to answer the question, and of course non-avian
dinosaurs survived the first wave. No one by Hollywood thinks that the
primary killing factor was the pressure wave. Rather, it was subsequent
effects (thermal pulse; impact winter; etc.) which led the the
environmental degradation which caused the devastation.


>4.) Is it possible that dinosaurs, pterosaurs and other inhabitants of this
planet about 108 Ma ago could be witnesses to the impact that created a
Tycho crater on the Moon? Would it be possible to see by a naked eye? Were
dinosaur eyes better equipped to see celestial bodies and events?

If that is the date of the Tycho crater, and if a dinosaur or pterosaur
was looking at the moon at that time, they certainly saw it. It is highly
doubtful the made much sense of it, but they saw it (in so far as photons
from the event would register on their retina and thus into the brain.)

> 5.) Was Moon really only about 10 arcseconds larger than it is today during
the Cretaceous? That's only about 1/10th of the size Man can recognize with
a naked eye. The difference is just 0,5 % or about 2000 kilometers. Could
somewhat bigger gravitational pull of the Moon affect non-avian dinosaurs?

Yes. The Cretaceous was ONLY 66 million years ago. And no, this is
essentially an insignificant difference in gravitational pull involved:
less than the difference between apogee and perigee of the moon today.

> 6.) Os it possible to calculate the positions of stars that form modern
constellations back in the cretaceous? Is there any such programme that can
do this? AFAIK the maximum is about 2 Ma now...

No, we can't. Too chaotic a system.

> What was the sky above Hell
Creek like? Was it red and dusty because of the vast amounts of sulphur and
ashes from the active volcanoes?

Just like the skies today. (Well, minus human contribution). After an
eruption it would be dusty; in between it would be blue skies.

> 7.) I've read an interesting article (http://www.osel.cz/index.php?clanek=
7954(http://www.osel.cz/index.php?clanek=7954)) where author states, that
Chicxulub impactor was an asteroid from the Flora family and that it would
first emerge on the Cretaceous sky three days (6 million kilometers away)
before the impact. Also interesting is the note, that the global temperature
(even on the other hemisphere) raised to at least 70 degrees Celsius. Is
this supported by firm evidence?

The first part: yes
(http://www.nature.com/nature/journal/v449/n7158/abs/nature06070.html)

The second part: no.
(http://gsabulletin.gsapubs.org/content/116/5-6/760.short) Estimates are
that the thermal pulse only raised ambient temperature by about 10 degrees
at most. However, if the thermal pulse issue was at play, it is IR
radiation delivered directly to the opaque bodies of animals and plants,
rather than an increase in air temperature, which was significant.

> 8.) Is it true, that we should consider M. W. De Laubenfels (1894 - 1960)
rather than Luis Walter Alvarez to be a true inventor of the first meteor-
killer hypothesis back in 1956? Or would geologists Allan O. Kelly and Frank
Dachille be first (they proposed their similar theory already in 1953)?

These folks proposed impacts as a cause, but utterly without any evidence
and with highly unrealistic and unlikely killing mechanisms. In contrast
the Alvarez team had evidence and a mechanism (impact winter) that is
reasonable.

Hope this helps.

Thomas R. Holtz, Jr.
Email: tholtz@umd.edu   Phone: 301-405-4084
Office: Centreville 1216
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
http://www.geol.umd.edu/~tholtz/
Fax: 301-314-9661

Faculty Director, Science & Global Change Program, College Park Scholars
http://www.geol.umd.edu/sgc
Fax: 301-314-9843

Mailing Address:        Thomas R. Holtz, Jr.
                        Department of Geology
                        Building 237, Room 1117
                        University of Maryland
                        College Park, MD 20742 USA