THE SEARCH FOR WATER AND LIFE ON MARS
-----------------------------------
John Pazmino
NYSkies Astronomy Inc
nyskies@nyskies.org
www.nyskies.org
2017 Novermber 15
Introduction
----------
i with several NYSkiers joined a full house at Simons Foundation
on 15 November 2017 for 'Search for water and life on Mars' by Dr James
wray, Georgia Institute of Technology and Geological society of
America. He is on several teams working with Mars spacecraft. The
lecture was a review of our present understanding of Mars water. He
explained he early clues, later confirmation, and present mystery of
water -- and possibly life -- on the Red Planet.
The quick summary is that Mars had mass water, open surface water
like seas and lakes and flowing water like rivers. Today Mars has at
least within observable reach only a minuscule amount of water, with
almost none in liquid form. As yet we found nothing of any past life,
like organic byproducts or fossils. The prospect remains open that
microbes can survive in subsurface habitats.
Any presentation about Mars, water, life, attracts heavy attention
from home astronomers, and also scientists in related fields. This one
was no exception; the auditorium was filled to capacity.
The talk began at 5:00 PM EST, preceded by a coffee-&-cookie snack
at 4:15 for the attendees. The lecture, like other Simons talks, was
free but advance registration is needed to ensure seating. When I
registered a few days earlier, I signed out a couple hours from my
workday.
On a mild day Simons is a brisk kilometer walk from my office
along Fifth Avenue. On the 15th it was a bit chilly, teasing me to do
a downtown 5th Av bus. I arrived at Simons at about 4:20 PM to face a
packed floor of scholars and scientists, all bantering about Mars.
I scooped up some grub from the snack counter and took a seat
among other guests. I looked around for other NYSkiers, catching a
few. We gathered together and noshed until the call rang out for the
lecture.
Simons foundation
---------------
Simons (SIGH-monz) Foundation supports many physical and medical
sciences, For one example, it partially funds the national Museum of
mathematics, a couple blocks away near madison Square. Among Simons
offerings is a weekly lecture on one of its disciplines. About eight
per year are valuable for home astronomers. NYC Events posts them upon
sufficient advance notice. Else they are noted in the NYSkies
yahoogroup. The audience for these talks is sprinkled with NYSkiers.
Simons Foundation is housed in a plain office building at 160
Fifth Av, Chelsea MH. It is common on Manhattan for buildings to take
yp an avenue address but have their entrances around the corner on the
cross street. In Simons's case, the entry is on 21st St thru a
curiously bland lobby fitted with only a service desk. In the yearend
holiday season this lobby sprouts a tall festive illuminated tree
and large wall-mounted wreath.
Simons is on the second floor, as only one of the building's many
other unrelated tenants, reached by stair or elevator. The floor's
public area has a central auditorium, peripheral snack alcove, and
restrooms. Before each lecture the guests enjoy a ha'hour of coffee-&-
cookies.
Altho the auditorium seats about 150 people, Simons asks for
advance registration by web or phone. Sometimes the hall is full with
registered audience. Standby arrivals wait outside for seats left
vacant by no-shows or cancellations.
The auditorium is modern, well appointed and furnished, with a
clever audience microphone system. In the back of the forward seat is
a panel for tuning on/off an embedded mike engage in the Q&A in an
audible voice. The very front row of seats have this feature in the
arm rest, where elbows can accidently turn it on.
Like for virtually all other lecture halls, no food or drink is
allowed. This is specially true at Simons since the audience enters
from the snack alcove with last bites of cookies. A short introductory
film about the auditorium is played before the talk that includes the
no-eat/drink warning.
Liquid water on Mars?
-------------------
Water as a chemical compound can exist in almost any place in the
solar system. The molecule, H2O, is extremely stable under ambient
conditions on all planets. We think certain satellites of Jupiter and
Saturn may have deep reserves of liquid water. We know of solid water
on other satellites and in comets.
On Mars, we are the presence of liquid water is marginal. We can
appreciate this from the phase diagram for water. A phase diagram
plots the physical state of a substance on a temperature-pressure
graph. The graph for water is crudely sketched in ASCII but a properly
rendered one is freely to hand from science webs.
+-------------------------------------------+
|\ PHASE DIAGRAM FOR WATER, H2O |
|\ |
| \ |
/|\ | \ + |
| | \ / CPP |
P | \ / |
| \ liquid / |
| | \ / gas |
| \ / |
| \ 0C / |
1|=======\========/=== Earth |
| \ 3C / 100C |
0.01|=========\===/====== Mars |
| \ / 15C |
| +TP |
| solid / |
| / |
+------------------------------------------+
---T--->
Each chemical substance is unique with its own phase diagram.
Altho the diagram probably can be generated thru physical chemistry or
chemical physics, the traditional method is brute force experiment.
For a given pressure P and temperature T water takes on one of its
three phases or states: solid, liquid, gas. In the specific case of
H2O there is a T-P point where all three states can coexist, the
Triple Point, TP in the diagram. There is also a point CP, the
Critical Point, where liquid and gas are no longer distinct phases.
The scales differ among authors. Temperature is in either Celsius
or Kelvin, C = K+273. The size of the degree is the same but K starts
at absolute zero while C is plus/minus from the freezing point of
water on Earth.
The pressure is one of several. it can be atmospheres, with
Earth's surface pressure being one. It can be in the physical units of
in bar or pascal. And it can be in units of some barometers, mm of
mercury.
It so happens that one atmosphere is very nearly one bar or 100
kiloPascal. It is also, more clumsy, 760mm. Home astronomers must be
conversant in all of these pressure schemes to follow news about
planetary explorations.
For Earth, 1 atmosphere, the double line across the graph cuts the
solid-liquid border at T = 0C or 273K. It cuts the liquid-gas border
at 100C or 373K.
On Mars, whose atmosphere pressure is 1/100 Earth's, the double
line passes a little above the Triple Point. It crosses a narrow zone
of liquid. Liquid water could exist between about 3C and 15C. A ground
temperature less than 3C freezes water into ice. hotter ground than
15C boils water into gas, Martian steam.
A typical maximum ground temperature on Mars in the equatorial
summer is 25C, falling to a typical night value of -75C. Even if there
was a pond of water, it would boil away by day or freeze at night.
Liquid water can only survive intermittently and momentarily.
At the poles in winter the temperature is insanely cold, around -
160C, freezing out just about all water, even from the mars
atmosphere, to form the polar caps. This degree of cold also
condenses carbon dioxide from the air, mixing with the ice in the
polar caps.
Properties of Mars
----------------
Mars is the only planet whose surface can be studied from Earth.
From the 1600s thru the mid 20th century we saw what could be an other
'earth'. Mars had dark regions for seas, bright ones for land, ice
caps at the poles, clouds, shifting 'vegetation', winds. We in the
late 1800s discovered what could be channels or canals, suggesting
that people on Mars built conduits to circulate water from the poles
and, OK, enable water-based navigation.
Astronomers and the public more or less assumed Mars was inhabited
with people, altho no one agreed what they were like. The Martians
ranged from friendly tribes ready for trade and business with Earth
all the way to hideous monsters coming after Earth to wipe out
humanknd. In fact, the Earth-like conditions on mars, derived from
our crude knowledge in the turn of the 20th century, convinced many
engineers and scientist to agitate for human space travel!
With no open water, Mars is entirely dry land. Mars is about 1/2
Earth diameter with about 1/4 Earth's surface area. Earth's surface is
about 1/4 land and 3/4 water. This ratio makes the total surface of
Mars about equal to the entire land area of Earth!
Mars shows no evidence of tectonics or ground quakes. On the other
hand Mars has several large extinct volcanos.
The surface has strong relief from deep valleys to tall mountains,
often exceding the extremes for these features on Earth. All
topography seems to be completed in the distant past, with no
evidence of significant modification in recent times.
The Martian craters a nd much of the overall topography seem
weathered like by bulk water and by aeolian forces.
The ground on Mars is almost globally reddish, like some deserts
on Earth. This tint comes from the content of iron oxide. We don't
know how this occurred.
There are hints that the axial tilt of Mars, now about 25 degrees,
was drasticly altered in the past. If correct, the modelling
of Mars's seasonal history could be severely complicated.
Water ice and dry ice sit on land in the polar regions. The ice
alternates poles for the winter/summer seasonal shift. From the early
20th century we figured out that the polar caps contain almost all of
any surface water on mars. This casually explained the need for the
network of canals to distribute this water thruout the planet.
Mars air is almost entirely carbon dioxide with a little water
vapor and traces of other gases. The water can condense into ice in
high elevation cirrus-like clouds. The water is far too scarce to
precipitate as rain or mist or fog.
The ground-level air pressure is 1/100 Earth's, yet it's enough
to loft up massive dust storms that at times blanket the whole planet.
In fact, these storms are the only physical action on an other planet
that can be observed by bare eye from Earth! Mars under a global storm
turns pale yellow, from its normal reddish hue. These color shifts
were noticed since antiquity without any clue for its cause.
Astrologers sometimes blended the Mars coloration in their fortune-
telling as a mysterious cosmic omen.
The thin air lets in solar radiation lethal to Earth-like life.
Ultraviolet ionizing radiation, plus cosmic rain of energetic nuclei,
sterilize the top layer of the Mars surface. The soil absorbs the
radiations, perhaps letting some life survive a meter or so below the
surface. The Scarce water in the air can not capture infrared
radiation to hold hear for the night or circulate around the planet.
Carbon dioxide, a;most the whole atmosphere, does not capture and
hold infrared waves; it is not really the 'greenhouse gas' on mars.
The result is that ground temperature at a given place under day/night
cycle swings thru about 100C. This, if not already killed by incident
radiation, would remove life from the surface that works on liquid
water. In the polar winter ground temperatures are incredibly low,
around -150C until the spring season.
Look for water
------------
All life as we understand it requires liquid water to convey
nutrients, effluent, heat, ions thruout the living organism. in humans
this water is mainly in the blood, with smaller amounts in digestive
fluids, gland secretions, lymph, body fat. A person, and other higher
lifeforms, die when internal water freezes under ambient conditions.
Please know well that presence of water does NOT prove presence of
life. It's the other way round. Absence of liquid water precludes the
existence of life, as suggested by ultra-dry places on Earth and every
where on the Moon.
The first visits to Mars by flyby spacecraft yielded no hint that
open surface water on Mars. Only a slice of the planet was imaged with
resolution of a couple kilometers.
The Viking landers applied chemical reagents on scooped up soil to
capture indications of life. The results were inconclusive.
Later flights were aimed at finding water, either now or in the
past. The evidence growed ever stronger that Mars in the remote pat
did have large regions of surface water. The first orbiting mapping
probes discovered what looked like rivers and lakes, all dried up now
but likely filled with water some time in the past.
The first positive proof of liquid water came with the Phoenix
lander in the mid 2-thous. Phoenix at the edge of the Mars polar cap
found water in scooped up soil. It internally heated the sample to
release water vapor. Phoenix also photographed aerial water condensing
into drops on its hull and struts.
The newest flights are seeking conditions m more than just
presence of water,that could ever sustain life on Mats. Possible
future missions may bring back samples of Martian soil for study in
labs with any number of tests and tools.
A false report of life on Mars came from certain meteorites
blasted off of Mars and falling on Earth. In them are vermicular
features that suggested fossils. After intense study these were
replicated with chemical methods not related to biological processes.
In all examinations it seems that lakes, rivers, other hydrology
prevailed on Mars several billion years ago, soon after the era of
massive asteroid collisions in the solar system. By some unknown
mechanism the bulk of this water vanished, leaving only minute
intermittent spots of water. Even the water as ice in the polar
regions is only a minuscule fraction of what likely flowed over the
planets in the remote past.
Yet the open water must have lasted for many millions of years
because we find layers of salt deposit here and there. These minerals
would accumulate over a long timespan.
Mars rovers
---------
Almost immediately after rolling off of their landing bases, the
rovers Spirit and Opportunity found positive evidence for mass water
in bygone eras. They imged and assayed minerals that could be formed
only in water, such as the 'blue berry' round stones and salt
crystals. Comparison with similar materials on the Moon, which never
had any mass water, showed that Mars minerals required water as a
formative agent. The lunar minerals were formed under utterly dry
conditions.
Rover Curiosity continues to verify the past presence of water.
Apparently water flowed on Mars after the cratering period because
Curiosity observed and studied 'bathtub rings', high-water residua, on
crater walls. The depressions were once filled with water.
Water releases
------------
Orbiting probes by now completely mapped Mars pole to pole to 6-
meter resolution. This is far better detail than any other planet's
mapping so far. Selected places are imaged to 30-cm resolution as
needed to study some important feature.
In the images there are occasional spurts of liquid water from a
slope that disappears on the next round or so of the satellite over
that location. It is plain unknown where this water comes from. Is it
from an underground cavity or aquifer? is it black ice mixed in soil
that melted? Is it some soil chemical taking in aerial water vapor
and then overflowing? Which is to say, these releases could come from
a source that's solid, liquid, or vapor!
There is no sure indication for a water cycle like on Earth. Water
apparently does not circulate from ground to air and back.
There is no precipitation of water any where on Mars. The ice at
the poles, mixed with frozen carbon dioxide, 'dry ice', condensed
directly from the water vapor in the air.
'Bathtub rings'
------------
Some Mars advocates are annoyed that the rovers are not
deliberately examining the salt deposits left in their vicinity by
water. Surely theses residua contain crucial clues -- if not positive
evidence -- of bygone life. Maybe they harbor vestigial microorganisms
in a tiny habitat. In the stead the rovers stand their distance and
use hands-off methods to explore the salts.
The deposits do look like similar ones on Earth that now harbor
microbes and tiny animicula. Possibly creatures on Mars could have
evolved to withstand the solar radiation and wide swings of daily
temperature.
The rovers keep away because they are not thoroly sterilized
against Earth life! They do not meet the current planetary-protection'
standards. There is the prospect that a rover tool may drop Earth life
into the salts and then mistake it for native Martian life. Worse, the
Earth life could flourish and contaminate the entire vicinity of the
salt deposit, upsetting all future explorations for Mars life.
Off-limits for humans?
--------------------
The frothing passion of many Mars advocates is to land humans on
Mars to both explore temporarily and to set up permanent colonies.
There are several companies working out paper scenarios for human
migration to Mars. None have any means what so ever for carrying out
their scheme, only a vague expectation that a national government will
magicly execute the plans for them.
Among planetary scientists the consensus is that humans should
stay off of the Red Planet. There is no way in hell a human, however
shielded from the Mars ecology, can avoid leaving contaminating
microbes, even germs and viruses, on the planet. Once this happens,
Mars is for ever trashed as a pristine world.
Suppose we do develop a suitable containment vessel for human
visitors? Then what's the point of sending humans to Mars? Altho they
will 'be on Mars' they can not in any casual way interact with it.
They may just as well be on Earth working a remote-control vehicle,
much as we already do now.
Humans could travel to Mars in an orbital or loop-around flight,
with no chance of transferring Earth life to the planet. Such would a
national prestige mission at first and thenafter tourist rides.
As a matter of practicality, given the pace of human space flight
any where in the world, it will be many decades before a human
expedition to Mars is fielded. The cost, even for a coalition of
countries, would be immense and the reward would be almost entirely
intangible, maybe at best a ticker-tape parade.
Conclusion
--------
Dr Wray went thru a thoro update on the situation of water on mars
and its relation to potential life, We know for sure Mars had
abundant open and flowing water billions of years ago. We know there
is some water left, sometimes in liquid form. We just don't know what
happened to the water in as much as we find no clues for some global
calamity to make the water vanish.
The question of mars as an abode of life remains open. If there is
life now it is of an extremely low-level form in perhaps isolated
underground pockets We so far find nothing like remains of past forms
of life, such as fossils or bones.
This lecture is timely for home astronomers for giving much-
welcome news for discussing Mars as it comes around to opposition in
summer 2018. Yjis is a favorable opposition, almost as good as that of
2003. Home astronomers with small scopes may discern the Martian
surface details. The planet looks so much like Earth! Do people live
there, too? Will we soon visit them? Or will they visit us?