The trouble with impacts

The trouble with impacts is that they tend to mess everything up, from the projectile to the target to the target chamber in the gun lab when I am investigating ice and water impacts. However, there is one case where the collection of material through impacts may have skewed the expected results from an investigation into the composition of a cometary nucleus to the changes in mineral composition as a result of impact shock.

The Stardust mission was a landmark for planetary sciences as it provided the first material to be collected and recovered from a comet.

Artist impression of Stardust Space crater http://stardust.jpl.nasa.gov/photo/artist.html

The spacecraft flew into the tail of comet Wild2 and collected material within the tail within aerogel, a synthetic porous silica gel where the liquid is replaced by gas making the material 98.2% air. This material captured the material within the tail of the comet and then travelled back to Earth.

The material from the comet was travelling at around 6.2 km/s when impacting the aerogel, and a lot of material also impacted the Al foil that lay on the grid securing the aerogel capture system.

Once the Spacecraft was back on Earth the material within the aerogel and foil craters were analysed to discover the composition of the nucleus of a comet.

However, one question that sat in the minds of people who investigate impacts such as myself was, how has the impact effects the composition of the material currently being analysed?

This is a rather big problem, shock from impacts is known to causing melting, devolitisation, and changes to the structure and event composition. Therefore is the composition of the material collected by stardust pristine or modified as a result of the impact. If modified then the science community is not investigating the composition of the comet but the results of shock-altered material.

What had to be done is experimentation within laboratory environments to understand the changes that had occurred to the Stardust material and to formulate the right corrections to make on the analysis results so that the composition of the comet can be determined.

This was undertaken by Foster et al, 2013 and Harriss et al, 2016. They took the material of known composition, Olivine, and fired it using the light gas gun at the University of Kent at the Aerogel and Al foils used on the Stardust mission at the same speed at the material is thought to have impacted the spacecraft collector ~6 km/s.

Impact crater on Foils from Olivine powder from Foster et al, (2013)

What was found was that when analysing the crater residue using RAMAN techniques the position of the Peaks of the unshot olivine grains did not match those of the olivine residues within the crater formed at a speed of ~6 km/s. This meant that the analyses by RAMAN of the Stardust grains would have produced incorrect compositional results and that a correction would be required.

This work only shows a correction is required for RAMAN analysis and has to this point only investigated the effects of olivine minerals. The next step would be to repeat these investigations using other minerals that have been located within the collected comet material including Enstatite.

MIR Space Station – 30 Years since the launch of Continued human habitation of Space!

The International Space Station is a marvel of engineering and science and has been the basis for international collaboration of 18 countries but it owes its success to the first module space station the Soviet Mir Space Station. Here is a short history of the Mir Space Station but for more information check out my article about the legacy of the Mir Space Station on the Conversation!

Mir was the first spacecraft to be assembled in space with a number of individual modules. The first three were launched between 1986 and 1989 before the fall or the USSR and the formation of a collaboration between the Russia and America.

1: Mir Core module – 19th Feb 1986

2: Kvant-1  – 1987

3: Kvant -2 – 1989

4: Kristall – 1990

Each of these modules were designed to undertake science investigation and experimentation, including, each of which allowed science research to be undertaken including astronomy, biological studies and growing food, all of which will show if humans are capable of undertaking, surviving and even thriving in space during long-duration flights to explore beyond the moon.

A view of the Russian space station Mir on 3 July 1993 as seen from Soyuz TM-17 Jean-Pierre Haigneré – http://www.spacefacts.de/graph/drawing/drawings2/soyuz-tm-17_mir_2.jpg

Post 1991 the collaboration between America and Russia formed the Shuttle-Mir Program where the shuttle was resupplied by the Space Shuttle and the Soyuz and manned by both Russian cosmonauts and American astronauts, the first of which arrived in 1995.

Over the next 11 years, the Mir space station would be hosts to American, ESA, Japanese and Ukrainian astronauts. Two new modules were added, Spektr with 4 solar arrays and equipment for Earth observation, and Priroda was the final module to be added in 1996.

A view of the US Space Shuttle Atlantis and the Russian Space Station Mir during STS-71 as seen by the crew of Mir EO-19 in Soyuz TM-21. http://grin.hq.nasa.gov/IMAGES/LARGE/GPN-2000-001315.jpg

A view of the US Space Shuttle Atlantis and the Russian Space Station Mir during STS-71 as seen by the crew of Mir EO-19 in Soyuz TM-21. http://grin.hq.nasa.gov/IMAGES/LARGE/GPN-2000-001315.jpg

In 1997 failures such as a collision with a resupply ship and fires on board meant that Mir was starting to show her age. Even after the ill-fated year the station was repaired and continued to be used until it was abandoned in 1999. It was in November 2000 that decommission of the Space station was announced. The deorbit of Mir began on Jan 24th, 2001 when the Space Station crashed into the South Pacific Ocean.

With the exception of a few months in 1989 Mir was permanently manned and the lessons learned from this continual habitation led to the development of the highly successful ISS and we now have a greater understanding of the effect the microgravity has on the biology of astronauts meaning that suitable technologies and regimes can be put in place for future long-duration missions into the depths of the Solar System.

How was the moon formed ? Hit and run, or one of the biggest impacts?

Our moon is an anomaly is more than one ways, firstly its the only moon with the dullest name just as Earth is Earth the moon of Earth is called Moon, even the Kerbles were creative with calling their the Mun!

Secondly its one of the only satellites bodies currently theorised to have originated from the body it orbits, unlike other moons which are either captured or produce from ancient ring systems.

However, the actual formation of the moon is still in debate with scientific research on the subject bringing published in science this week.

It is generally accepted that the formation of the moon and the spin on the Earth on its axis are linked and that it was an impact between two bodies, a larger Earth and the Mars-size Theia that produced both these phenomena,

The impact between the two planets caused major disruptions of both bodies and flung debris from the collision into an orbit around the crippled planet. Over time the debris comes together and forms the moon and the initial collision disrupts the rotation of the Earth so that it moves are a slower rate the previously.

There have been links between the Earth and the moon ever since Apollo astronauts brought back samples of Moon rock to analyses. The composition of the moon is similar to that predicted of a Young Earth. since the formation of the moon, the Earth dynamic internal heating has changed and evolved the planet’s crust through millennial of plate tectonics. Whereas the moon becomes dormant and still.

A second and most important of the evidence for the Earth and Moon originating from on body is the oxygen isotope composition.

Oxygen isotopes are used as a characterization for the different planetary bodies of the Solar System. Each meteorite family, asteroid and planet has a singular oxygen isotope composition with a few overlaps. It is this which allows scientists to discover the original of Martian and Lunar Meteorites and group other meteorites into logical families.

 

The oxygen isotope composition of the rock brought back from the Moon sits on what in the trade is known as the Terrestrial Fractionation Line. This TFL is the line on which all rocks from Earth fall, along with the lunar samples suggesting that the Moon and the Earth originate from the same or similar body.

However this is the crux of the matter, Earth and Moon rocks are similar but my own experiments have shown the impressive survivability of the smaller objects during an impact. Therefore the question is: Where is the material from Theia?

Recent work investigating the oxygen isotope composition of Lunar Rocks suggest that the Moon and Earth have near identical Theia contents due to their indistinguishable oxygen isotope composition meaning that the moon-forming impact thoroughly mixed and homogenized the oxygen isotopes of Theia and the early Earth (Proto-earth).

Therefore there was no Hit and run collision but a high energy, high – angular -momentum impact that mixed the material of Theia with he Proto Earth distributing it homogeneously in the newly formed Moon and Earth.

 

 

Thoughts from an Impact conference

In late September I attended the Bridging the Gap Conference 2015 hosted by The University of Freiburg in Germany.

Bridging the Gap III

This was a small conference specializing in all aspects of impact cratering research and aimed to bring together the three main fields of impact cratering research together. These are:

1. Laboratory based research, such as that undertaken here at the University of Kent;

2. Fieldwork based research, where geologists investigate the outcrops of terrestrial impact craters and the remote sensing of extra-terrestrial caters;

3. Computational modelers that use software to simulate different impact scenarios and environment development.

All these fields provide vital information to the research of impact cratering but for a full understanding the three fields must work together and learn from the research of one another. Hence the Bridging the gap conference.

This three day conference included a number of oral sessions ranging from discussion the fate of the projectile, (where Jamies‘ work was presented) to target properties (where I presented my work relating to ice targets) to discussions of suevites, glasses and melt rocks.

Over all the talks were engaging and informative, with chances for discussion of different topics over coffee and lunch.

One talk of interest discussed the idea of using accessory minerals as indicators of shock in impacted rocks, given by colleagues at the University of Portsmouth who we shall bee looking forward to collaborating with on this work. In addition the a proposal for a new Shock pressure Classification scheme highlight sciences dependence of the known and well used methods of classification thought with new developments in the field many of these old classification schemes become ill defined and require extension or revision.

Interesting work looking at the impact related winds on Mars introduced me to a new phenomenon which was wonderfully explained and discussed.

Major discussion about acoustic fluidisation and what actually is a sueavite provided entertaining discussions though out the whole conference.

Overall this conference were wonderfully put together and really did provide a change for myself and the other attendees to discuss ideas, get feed back and develop collaborations with those that investigate Impact cratering in a completely different way.

The modellers provided a wonderful morning show the rest of us what can actually be achieve using the software iSale 2, which was highly informative and interested for many of the non-modelers including myself.

To conclude I wish to say congratulation to the Thomas Kenkmann and all the conveners and the science organizing committee for putting on a great, informative conference with a great conference dinner overlooking the beautiful city of Freiburg.

 

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Welcome to Science with a Big Gun!

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This blog aims to update the world monthly on the Space science research being undertaken by the Center for Astrophysics and Planetary Science at the University of Kent.

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