by Linda Moulton Howe

March 2013

from EarthFiles Website
 

 

 


“One can make a pretty cogent argument that life might
have been started initially on Mars and then perhaps 4 billion years
ago came to Earth as a result of these natural impacts.”
- Jay Melosh, Ph.D.



 

 


The dark disc is the Martian moon Phobos transiting between
Mars and the Sun, as seen by Mars Rover Opportunity on March 10, 2004.
Image frame from: VIDEO NASA March 10, 2004, Opportunity.

 


Martian moon Phobos with its Stickney Crater is considered
a “captured” asteroid with low density that is in an unusual circular
and low orbit around Mars. Image by NASA's Viking 1 Orbiter in 1977.

 



March 1, 2013

West LaFayette, Indiana

Phobos and Deimos are the two moons that orbit Mars.

 

Phobos is notoriously strange and small - only about 17 miles long and 11 miles wide, shaped a bit like a potato. Phobos is one of the darkest bodies in our solar system with composition similar to carbonaceous chondrites, the space rocks that contain higher percentages (3% to 22%) of water as well as organic compounds.

 

Adding to the mystery is that Phobos has an unusual circular orbit that is very close to Mars, puzzling planetary scientists about how that occurred since most solar system bodies do not have circular orbits.

 

Phobos moves around Mars faster than Mars itself rotates. That's why Phobos rises and sets twice each Martian day. The Phobos orbit is so low that its angular diameter as seen from the surface of Mars varies visibly as its position moves in the sky.

 

Further, Phobos's density is too low to be solid rock, sparking speculation that Phobos is not only porous, but is hollow and perhaps even an artificial construction.

Recently a web article came to Earthfiles, along with an illustration of how Phobos is camouflage for a structured interior. Allegedly the information source was someone inside the European Space Agency, known as ESA.

 

No one at ESA has confirmed any reality to the illustration and web article, but I was provoked to research more about Phobos and I discovered a June 28, 2012, Purdue University article entitled, “Evidence of Life on Mars could come from Martian moon Phobos.”

 

Quoted in the Purdue University article is Jay Melosh, Ph.D., Distinguished Professor of Earth, Atmospheric and Planetary Sciences; and Physics and Aerospace Engineering.

 

Prof. Melosh said,

“A sample from the moon Phobos, which is much easier to reach than the surface of the Red Planet itself, would almost surely contain Martian material blasted off from large asteroid impacts hitting Mars.

 

If life on Mars exists, or existed within the last 10 million years, a mission to Phobos could yield our first evidence of life beyond Earth.”

I called up Prof. Melosh to ask him about his Phobos hypothesis that the moon's dust could have signs of life from Mars plus the circulating web article about an alleged ESA leak concerning a hollow, artificially constructed Phobos.

 

He surprised me with news that the European Space Agency is planning to launch a spacecraft to Phobos on a pioneering mission to bring Phobos dust back to Earth laboratories for hands-on analysis beyond the Curiosity rover's search for evidence of life on the Martian surface - past, present or both.

 

I asked Prof. Melosh when ESA plans to launch the Phobos sample return mission.
 

 


Interview

 

 

 

NASA's Planetary Protection Office chose a team of Purdue
University researchers to evaluate whether a sample from the
Martian moon Phobos could contain enough material from Mars
to include viable Martian organisms. Prof. Jay Melosh stands
next to a digital illustration of possible particle trajectories from
an asteroid impact on the red planet, Mars, that can end up on
low-circling Phobos. Image by Purdue University/Mark Simons.

 


 

 

 

 

 

 



Jay Melosh, Ph.D., Prof. of Earth, Atmospheric and Planetary Sciences; and Physics and Aerospace Engineering at Purdue University, West LaFayette, Indiana:

“We're probably talking about something in the 2020s, if we do have a sample return mission from Phobos.

 

Now, you might ask why do we want to bring a sample back from Phobos? Why not bring one back from Mars. The answer to that is simply a matter of propulsion capability.

 

It's very, very difficult to run a mission in which we land a spacecraft on the surface of Mars that's big enough to get off the Martian surface and back to Earth.

On the other hand, Phobos is already in orbit around Mars. It's much easier to plan a mission with chemical propulsion where we rendezvous with Phobos, grab a sample and then come back to Earth.
 

 


THE EUROPEAN SPACE AGENCY IN TERMS OF IT WORKING ON A PLAN TO GO TO PHOBOS TO TRY TO GATHER MATERIAL, DOES IT ALSO FIT INTO INFORMATION THAT HAS BEEN CIRCULATING ON THE WEB SAYING THAT THE EUROPEAN SPACE AGENCY IS DESCRIBING PHOBOS AS HOLLOW. AND IN THESE WEB REPORTS, IT IS RAISING THE QUESTION: COULD PHOBOS BE A CONSTRUCTED OBJECT AND WAS NOT NATURAL?

I have not seen those web reports. But there is absolutely nothing that I know of that indicates that Phobos is not a natural object.



Mysteries of Phobos
But there are some mysteries with Phobos.

 

We don't know how it got into orbit around Mars. We don't know - it's composition seems to be like a primitive meteorite (carbonaceous chondrite), which would mean that Phobos was captured. We don't know any way that could happen in the absence of quite a bit of gas being around, which would put its capture very early in the solar system.

So, how it got into the orbit it's got is kind of a mystery.

 

But looking at the surface of Phobos, looking at its mass, which we know - we've had many close spacecraft encounters. Its density is relatively low, but then it's full of fractures. What we see is not out of line with it being a kind of ordinary chondrite that has been fractured.

 

The lines across the surface of Phobos are just regolith draining into gaping fractures. So, its (low) density is not terribly much of a surprise. I don't know what those web reports are, but I would not pay too much attention to them.
 


(Editor's Note: Wikipedia - Regolith is a layer of loose, heterogeneous material covering solid rock. It includes dust, soil, broken rock, and other related materials and is present on Earth, the Moon, Mars, some asteroids, and other terrestrial planets and moons. The term regolith combines two Greek words: rhegos, “blanket,” and litho, “rock.”]



Is Phobos “Hollow”?


THE SOURCE IS SUPPOSED TO BE SOMEBODY AT ESA AND I'M WONDERING, WHEN THEY USE THE WORD ‘HOLLOW,’ WHAT DOES THAT MEAN TO YOU AS A PLANETARY GEOLOGIST?

A hollow configuration is something that does NOT occur naturally. I suppose that's where the speculation comes from. I would say that Phobos is thoroughly fractured and has a lot of void space in it.

 

That doesn't imply anything artificial.

Phobos is a very peculiar situation. It's closer to its planet Mars than what is called the Roche Limit. Tidal forces are actually tending right now to tear Phobos apart. It doesn't have very much life left on a geological timescale. We expect that as tides cause Phobos to spiral in towards Mars, within 100 million years or so, Phobos will be ripped apart and Mars will have a ring sort of like Saturn's rings for awhile.

 

But that doesn't imply anything artificial. Phobos has probably been spiraling towards Mars for most of its life time.
 


[Editor's Note: Wikipedia - The Roche limit, sometimes referred to as the Roche radius, is the distance within which a celestial body, held together only by its own gravity, will disintegrate due to a second celestial body's tidal forces exceeding the first body's gravitational self-attraction. Inside the Roche limit, orbiting material will tend to disperse and form rings, while outside the limit, material will tend to coalesce. The term is named after Edourd Roche, the French astronomer, who first calculated this theoretical limit in 1848. ]
 

 


BEYOND THE DESCRIPTION OF LIGHT DENSITY AND MIGHT BE HOLLOW, WHAT ARE OTHER PECULIARITIES?

Well, from what we can tell from its detailed spectrum, colors it reflects, it appears to be most closely related to a primitive meteorite - doesn't look like the surface of Mars at all. It appears to have been captured, perhaps from the asteroid belt.

 

But nevertheless, it's in a circular orbit and that does not happen very naturally. So, there are a number of curious things about Phobos, but again, nothing suggesting it's artificial.
 

 


HOW DOES PHOBOS COMPARE TO DEIMOS?

Well, Phobos is bigger than Deimos and it's closer to Mars than Deimos. The reflectance spectrum between Phobos and Deimos is quite similar. Phobos is a little more difficult to get to. It's further down in Mars's gravity well. But Deimos is not inside the Roche Limit and it doesn't have the striations across the surface that Phobos does. So in appearance, it looks quite a bit different.



Phobos Source Is Unknown

IF PHOBOS IS A CAPTURED OBJECT, THAT MEANS THAT NO PLANETARY GEOLOGIST IS EVER GOING TO BE ABLE TO KNOW PRECISELY WHERE PHOBOS CAME FROM?

That's probably true of just about any captured object.

 

It's certainly related to things in the asteroid belt, but that's one of the reasons it's so interesting to bring back a sample to see what it's relations to other objects in the asteroid belt actually are. Deimos would also have been captured. It's also in a circular orbit and has the same problems of where is its origin as Phobos.

 

So they are both peculiar in that sense.

We know that Jupiter and Saturn have a large number of so-called irregular satellites that look like they have been captured, but none are in circular orbits and none is close to their primary (planet) as Deimos and Phobos are.
 

 


FROM YOUR POINT OF VIEW AS A PLANETARY GEOLOGIST, HAVE YOU HAD ANY DISCUSSIONS EVEN IN CASUAL CONVERSATION WITH ANY PLANETARY GEOLOGIST AT ESA ABOUT THE POSSIBILITY THAT ALL THESE PECULIARITIES OF PHOBOS MIGHT INDICATE THAT IT'S SOME LEFT OVER CONSTRUCTION FROM SOMETHING FROM OUTER SPACE?

I've not had any such conversation at all. I've had many conversations with people in ESA and with people involved in spacecraft exploration of Mars and there is no serious discussion that Phobos is any thing other than a natural object.



Odds for Life Evidence in Phobos Dust?

WHAT IS YOUR BEST SPECULATION TODAY ABOUT WHETHER OR NOT YOU WOULD FIND SOME FORM OF LIFE IN MATERIAL COLLECTED FROM PHOBOS?

We get meteorites from Mars all the time. About one ton of Martian surface material falls into the Earth's atmosphere every year kicked off by impacts on the surface of Mars.

 

In fact, one can make a pretty cogent argument that life might have been started initially on Mars and then perhaps 4 billion years ago came to Earth as a result of these natural impacts.
 

 


IS THERE AN ARGUMENT FOR WHY CURIOSITY (ROVER) WOULD NOT FIND MICROBIAL LIFE ON MARS?

Well, you could say that life never got started on Mars, although the evidence is it was once as hospitable - or more so - than the Earth through conditions in which life might form.

 

But we don't know the circumstances under which life forms. It might be a rare and happy accident that just happened to have occurred on Earth. Or it might be it occurs whenever conditions are right.

Now, the surface of Mars is an extremely dry, cold, hostile desert that's bathed in ultraviolet light that is lethal to any terrestrial organism. It's not a place where at least Earth-type life could thrive now.

 

But it might be that life got started in the past (on Mars) and that's the point of the Curiosity rover investigation to find out if there is evidence of past life; and even better, if there is something still surviving deep below the surface.
 

 


I THINK YOU SUGGESTED EARLIER THAT THERE IS A POSSIBILITY THERE MIGHT HAVE BEEN METEORITES THAT MADE IT FROM MARS TO EARTH IN EARTH'S DISTANT PAST THAT COULD HAVE STARTED LIFE HERE?

That's right. That is a possibility.

 

It's a speculation, but it's based on the fact that we have Martian meteorites that came to us from Mars without any alteration and under conditions that life could have survived. It appears that Mars had a stable crust and flowing water perhaps earlier than Earth's moon existed and perhaps earlier than when Earth was hospitable for life.

 

That would have been about 4 billion years ago.
 

 


SO THAT MIGHT HAVE HAPPENED WHILE THERE WERE LAKES AND RIVERS ON MARS.

That's exactly right.
 

 


IF THAT'S THE CASE AND THERE MIGHT HAVE BEEN LIFE ON MARS DEVELOPING, WHAT DO YOU THINK COULD HAVE HAPPENED THAT WOULD HAVE CHANGED THAT WATERY LIFE CONDUCIVE PLANET TO THE COLD DESERT THAT IT IS NOW?

Well, Mars evidently lost most of its atmosphere.

 

Meteorite impacts themselves eject a certain amount of the atmospheric gas. The solar wind impinges directly on the atmosphere of Mars unlike the Earth because Mars presently lacks a magnetic field. It once had a magnetic field that would withstand the solar wind.

 

But Mars cooled off faster. Its core froze and its dynamo died and the magnetic field died at the same time. That allowed the solar wind to directly hit the atmosphere, which would have stripped off quite a bit of it as well as the ultraviolet hitting directly on the surface.

Earth has a pretty good shield of water loss by ultraviolet light in the form of ozone. The ozone shield for the Earth comes from oxygen.

 

So life developed on Earth to the point that it started producing oxygen that has since about 2.5 billion years ago been a shield against the evaporation of water, whereas that is not the case with Mars.



Did Earth Life Originally Come from Mars?

 

Mars photographed

 by the Hubble Space Telescope.
 


WHAT IS THE MOST EXCITING PART OF YOUR RESEARCH IN THIS SOLAR SYSTEM NOW?

The excitement is:

  • What did the large number of impacts in Earth's early history do to Earth?

  • Where did life come from?

  • Did life on Earth come from Mars and how did life start?

  • What's the relation of life to the large impacts that we know were occurring?

 


WHAT IS YOUR PERSONAL THINKING NOW IN FEBRUARY 2013 ABOUT WHAT YOU MOST STRONGLY THINK MIGHT BE THE ORIGIN FOR LIFE ON THIS PLANET?

I think the ultimate origin is chemical; that is, we had an environment in which carbon in particular had an opportunity of interacting with other elements and an environment that changed constantly would have gone through a chemical evolution where the chemicals that grow faster get to be more abundant than the chemicals that don't grow so fast.

 

Eventually they evolved into what we recognize as life.
 

 


FINALLY, DO YOU HAVE A BET WITH ANY OF YOUR PLANETARY GEOLOGIST COLLEAGUES ABOUT CURIOSITY FINDING LIFE ON MARS?

I have no such bet. (laughs) I have a fond hope that Curiosity will find life, but I think it's possible it will not.
 

 


AND IF IT DOESN'T, WHAT WOULD YOUR REACTION BE?

Disappointment.”




On February 8, 2013, this first Curiosity Rover self-portrait panorama was captured at the
John Klein drilling site after the first shallow drill test hole was conducted in Gale Crater
(foreground hole). This panoramic mosaic was constructed using frames from Curiosity's
“Mars Hand Lens Imager” (MAHLI) and Mastcam. The MAHLI frames used to create
the self-portrait exclude sections that show the arm itself, making the rendering system
invisible in the composition. For the full experience, you can go:
here to view the 360-degree Curiosity panorama image.