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01/11/2006

Mars and Moon - Past and Present

Last week I mentioned that fraudulent fellow named Hwang and
dashed hopes for a major breakthrough in stem cell research.
When I wrote the column, I hadn’t read my December Scientific
American, which named Hwang “Researcher of the Year” for
2005. In his Week in Review columns on this Web site, Brian
Trumbore often says to wait 24 hours; in science it takes a bit
longer, say a month! This week, let’s be more positive and
consider some scientific ventures that have far exceeded
expectations, the spacecraft and rovers either circling or crawling
on the surface of Mars. The international teams working with
NASA/JPL and the European Space Agency (ESA) have reasons
to be very proud of their achievements. Visits to the Web sites
of ESA and JPL provided much of the material below.

The rovers Spirit and Opportunity have been wandering around
Mars for two years, much longer than they had been expected to
survive. Opportunity has traveled 4 miles, up and down slopes
and in and out of situations where its wheels were stuck, thanks
to its expert drivers back on Earth. Today, the hardy little
traveler is headed for Victoria Crater, a half mile wide crater
where layers of Mars’ geological past are exposed. Both Spirit
and Opportunity have delivered on the hope that they would
confirm the presence of water in Mars’ past. They identified
hydrated minerals that contain molecules of water in their
structure and found areas that are thought to have been pools of
water a long time ago.

There was a downside to these findings, however. The minerals
that were found were of a type that must have formed from
highly acidic pools of water, not the sort of condition favorable
for life. Although, here on Earth, various kinds of organisms
have been shown to thrive under surprisingly hot and acidic
conditions, scientists would feel more comfortable if there had
been a period on Mars that was not so acidic.

Here’s where ESA and its Mars Express orbiter comes into the
picture. Mars Express contains two instruments of note here –
OMEGA and MARSIS. With both infrared and visible light
capabilities, OMEGA can both see and identify the minerals that
appear on the surface of Mars. OMEGA sees a lot of hydrated
sulfates that are formed from those acidic solutions. But last
March the OMEGA team revealed that OMEGA had also spotted
outcroppings of hydrated minerals known as “phyllosilicates”;
one example of a phyllosilicate is clay. Clays form, not from
acidic solutions, but from neutral or alkaline solutions.

At a meeting last month of the American Geophysical Union, the
OMEGA team announced they had found layers of the clays
underneath layers of the sulfates. They say that their findings are
consistent with a scenario in which, around 3.8 billion years ago,
there was lots of water that reacted with the rocks/minerals on
Mars to form the clays. There was mud on Mars. If life did form
on Mars, this would have been the most propitious time. It also
would have been about the same time that life first appeared on
Earth. Later, on Mars, conditions became more hostile and the
acidic times prevailed.

According to an article by George Musser in the December
Scientific American, Diana Blaney of JPL reported at a meeting
in September of the American Astronomical Society that Spirit
had looked at a rock dubbed Independence and found it to be
claylike. Why the keen interest in clays, aside from the fact that
they typically form in neutral or alkaline, not acidic solutions? I
think that I’ve mentioned in the past that some workers have
shown that clays promote reactions that form chemical
compounds necessary for life and that clays may even provide
templates for the formation of structures resembling cell walls.

What about water on Mars today? If astronauts ever do arrive on
Mars, it would be great if they didn’t have to carry all the water
to satisfy their needs. A known supply of water would certainly
come into play in the selection of a landing site, I should think.
Here’s where ESA’s MARSIS comes in. MARSIS (Mars
Advanced Radar for Subsurface and Ionospheric Imaging) has
been used to study both the Martian atmosphere and what lies
under the Martian surface. By studying the echoes of returning
radar waves, the researchers have found hidden impact zones that
formed when Mars was struck by space objects early on in its
history. These impact zones were filled in with material from
winds, lava flows, etc.

The MARSIS team found evidence that the impact basins may be
filled in partially with water-ice mixtures. However, more
spectacular was what they found when they looked in areas
around Mars’ north pole. Radar reflections showed a likely layer
of nearly pure water-ice that is over a half-mile thick. If I went
to Mars, I sure would try to land somewhere near that big chunk
of ice. Without having to carry extra water, there might be room
for the ingredients for a celebratory Scotch or bourbon on the
rocks after the long trip from Earth!

Another orbiter is NASA’s Mars Global Explorer. Michael
Malin, of Malin Space Science Systems in San Diego, has a
camera onboard the Explorer. His camera revealed a mystery
that was discussed at the December meeting. There are hundreds
of craters on Mars that are filled with some kind of sediment;
some are filled to overflowing. The mystery is not only where
did the sediment come from but in many of them sediment has
been removed so the there are mounds of sediment in the craters.
One striking example is the nearly 100-mile wide Henry Crater
near Mars’ equator.

The Henry crater has a mound of sediment that is over a half
mile high, higher than the rim of the crater. The mound of
sediment has distinct layers that match the layers of sediment
sticking to the walls of the crater. Was the sediment laid down
by wind, seas or what? Has wind been responsible for removing
the sediment, forming the mounds? Nobody at the meeting had a
solution. Hopefully, the Mars Reconnaissance Orbiter,
scheduled to arrive over Mars in March with a higher resolution
camera, will provide clues to solve this mystery.

Although not related to the Mars, a Mars-size object is believed
to have hit Earth early on in its history, the result being that
debris from the collision ended up orbiting Earth and forming
our Moon. In the collision, Earth is thought to have picked up
perhaps 10 percent of its mass from the Mars-size intruder.
Although other objects have struck and are still striking our
planet, this collision is thought to be the last truly monumental
batch of material incorporated into our Earth. Thorsten Kleine in
Germany and his colleagues from Germany, Switzerland and the
UK have an article in the December 9 Science that sheds light on
when this huge event took place.

Initially, both the Moon and Earth were molten and what Kleine
and coworkers have done is to date the time when the molten
magma cooled down and crystallized. By dating that time, they
can also come up with a date for Earth’s last big grab of material.
I won’t go into detail on their work except to say that it involves
measuring the amounts of different isotopes of the metals
hafnium, tungsten and tantalum in samples of metal and rocks
supplied by NASA. I assume that the samples were collected by
our astronauts back in the days when we were walking on the
Moon. The researchers’ results indicate the moon crystallized
4.53 billion years ago, the big collision taking place some 30 to
50 million years after the formation of the solar system.

December’s been a good month for learning about the past and
present of our planet and two of our solar system companions.

Allen F. Bortrum



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-01/11/2006-      
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Dr. Bortrum

01/11/2006

Mars and Moon - Past and Present

Last week I mentioned that fraudulent fellow named Hwang and
dashed hopes for a major breakthrough in stem cell research.
When I wrote the column, I hadn’t read my December Scientific
American, which named Hwang “Researcher of the Year” for
2005. In his Week in Review columns on this Web site, Brian
Trumbore often says to wait 24 hours; in science it takes a bit
longer, say a month! This week, let’s be more positive and
consider some scientific ventures that have far exceeded
expectations, the spacecraft and rovers either circling or crawling
on the surface of Mars. The international teams working with
NASA/JPL and the European Space Agency (ESA) have reasons
to be very proud of their achievements. Visits to the Web sites
of ESA and JPL provided much of the material below.

The rovers Spirit and Opportunity have been wandering around
Mars for two years, much longer than they had been expected to
survive. Opportunity has traveled 4 miles, up and down slopes
and in and out of situations where its wheels were stuck, thanks
to its expert drivers back on Earth. Today, the hardy little
traveler is headed for Victoria Crater, a half mile wide crater
where layers of Mars’ geological past are exposed. Both Spirit
and Opportunity have delivered on the hope that they would
confirm the presence of water in Mars’ past. They identified
hydrated minerals that contain molecules of water in their
structure and found areas that are thought to have been pools of
water a long time ago.

There was a downside to these findings, however. The minerals
that were found were of a type that must have formed from
highly acidic pools of water, not the sort of condition favorable
for life. Although, here on Earth, various kinds of organisms
have been shown to thrive under surprisingly hot and acidic
conditions, scientists would feel more comfortable if there had
been a period on Mars that was not so acidic.

Here’s where ESA and its Mars Express orbiter comes into the
picture. Mars Express contains two instruments of note here –
OMEGA and MARSIS. With both infrared and visible light
capabilities, OMEGA can both see and identify the minerals that
appear on the surface of Mars. OMEGA sees a lot of hydrated
sulfates that are formed from those acidic solutions. But last
March the OMEGA team revealed that OMEGA had also spotted
outcroppings of hydrated minerals known as “phyllosilicates”;
one example of a phyllosilicate is clay. Clays form, not from
acidic solutions, but from neutral or alkaline solutions.

At a meeting last month of the American Geophysical Union, the
OMEGA team announced they had found layers of the clays
underneath layers of the sulfates. They say that their findings are
consistent with a scenario in which, around 3.8 billion years ago,
there was lots of water that reacted with the rocks/minerals on
Mars to form the clays. There was mud on Mars. If life did form
on Mars, this would have been the most propitious time. It also
would have been about the same time that life first appeared on
Earth. Later, on Mars, conditions became more hostile and the
acidic times prevailed.

According to an article by George Musser in the December
Scientific American, Diana Blaney of JPL reported at a meeting
in September of the American Astronomical Society that Spirit
had looked at a rock dubbed Independence and found it to be
claylike. Why the keen interest in clays, aside from the fact that
they typically form in neutral or alkaline, not acidic solutions? I
think that I’ve mentioned in the past that some workers have
shown that clays promote reactions that form chemical
compounds necessary for life and that clays may even provide
templates for the formation of structures resembling cell walls.

What about water on Mars today? If astronauts ever do arrive on
Mars, it would be great if they didn’t have to carry all the water
to satisfy their needs. A known supply of water would certainly
come into play in the selection of a landing site, I should think.
Here’s where ESA’s MARSIS comes in. MARSIS (Mars
Advanced Radar for Subsurface and Ionospheric Imaging) has
been used to study both the Martian atmosphere and what lies
under the Martian surface. By studying the echoes of returning
radar waves, the researchers have found hidden impact zones that
formed when Mars was struck by space objects early on in its
history. These impact zones were filled in with material from
winds, lava flows, etc.

The MARSIS team found evidence that the impact basins may be
filled in partially with water-ice mixtures. However, more
spectacular was what they found when they looked in areas
around Mars’ north pole. Radar reflections showed a likely layer
of nearly pure water-ice that is over a half-mile thick. If I went
to Mars, I sure would try to land somewhere near that big chunk
of ice. Without having to carry extra water, there might be room
for the ingredients for a celebratory Scotch or bourbon on the
rocks after the long trip from Earth!

Another orbiter is NASA’s Mars Global Explorer. Michael
Malin, of Malin Space Science Systems in San Diego, has a
camera onboard the Explorer. His camera revealed a mystery
that was discussed at the December meeting. There are hundreds
of craters on Mars that are filled with some kind of sediment;
some are filled to overflowing. The mystery is not only where
did the sediment come from but in many of them sediment has
been removed so the there are mounds of sediment in the craters.
One striking example is the nearly 100-mile wide Henry Crater
near Mars’ equator.

The Henry crater has a mound of sediment that is over a half
mile high, higher than the rim of the crater. The mound of
sediment has distinct layers that match the layers of sediment
sticking to the walls of the crater. Was the sediment laid down
by wind, seas or what? Has wind been responsible for removing
the sediment, forming the mounds? Nobody at the meeting had a
solution. Hopefully, the Mars Reconnaissance Orbiter,
scheduled to arrive over Mars in March with a higher resolution
camera, will provide clues to solve this mystery.

Although not related to the Mars, a Mars-size object is believed
to have hit Earth early on in its history, the result being that
debris from the collision ended up orbiting Earth and forming
our Moon. In the collision, Earth is thought to have picked up
perhaps 10 percent of its mass from the Mars-size intruder.
Although other objects have struck and are still striking our
planet, this collision is thought to be the last truly monumental
batch of material incorporated into our Earth. Thorsten Kleine in
Germany and his colleagues from Germany, Switzerland and the
UK have an article in the December 9 Science that sheds light on
when this huge event took place.

Initially, both the Moon and Earth were molten and what Kleine
and coworkers have done is to date the time when the molten
magma cooled down and crystallized. By dating that time, they
can also come up with a date for Earth’s last big grab of material.
I won’t go into detail on their work except to say that it involves
measuring the amounts of different isotopes of the metals
hafnium, tungsten and tantalum in samples of metal and rocks
supplied by NASA. I assume that the samples were collected by
our astronauts back in the days when we were walking on the
Moon. The researchers’ results indicate the moon crystallized
4.53 billion years ago, the big collision taking place some 30 to
50 million years after the formation of the solar system.

December’s been a good month for learning about the past and
present of our planet and two of our solar system companions.

Allen F. Bortrum