Every so often with this blog we shall be looking at the ongoing work of one of the members of the Impact Group at the University of Kent.

First under the spot light is Jamie, a first year PhD Student who is about to start his second year but already has a lot of data and plans for his project.

Following on from the last post about the survivability of a projectile during high velocity impacts which is a subject currently not well represented in the literature, Jamie’s project is doing just that investigating the breakup of basalt projectile when impacted.

Aim of Research

The main aim of his research is to discover the state of survival of the basalt projectile at different impact speeds which lead to different levels of shock experienced by the projectile.

Why are projectile fragments important?

Projectile material has been recovered form 13 sites on earth and may form dark region on asteroids such as Vesta and non-indigenous material has been fund on the moon and recovered from inside meteorites. So there is clear evidence that the projectile can survive these real life impact and so understanding the break up and survivability of different types of impact material can help in our understanding of the development of the bodies in the Solar System.

Data collection method

He used the two stage light gas gun (see previous posts) to fire basalt cubes (hand filed by Jamie) at speed between 0.5 and 6.0 Km/s into a target of water.

The water target holder with water ready to go into the chamber

This may not be a realistic impact but it provides the expected range of shock pressure for the projectile to experience. 

The water is collected and filtered to extract the fragments of basalt projectile that have survived the impact. The fragments are measured and recorded using a Scanning electron microscope (SEM) which allows imaging of the micron sized particles of basalt.

Jamie working on his projectiles in the Lab ~(Source – University of Kent)

Whats the big picture here?

A novel look into the survivability of basalt at high shock pressures to render the projectile survival percentage. This can be used to compare to the amount of projectile surviving impacting on different solar system bodies. Furthermore, a look into the evolution of cumulative fragment size distributions with increasing peak shock pressure.

Jamies work will soon be presented at the up coming Bridging the Gap conference in Frieberg, Germany.

During impact cratering at hyper velocity speed  (>3 km/s) the event experiences such high energies that the resulting crater provides so much information, but what about the projectile?

It seems implausible that a small projectile would produce so much destruction and then survive, but the survival of part of the projectile is required for theories of some of the fundamental questions about the beginnings of our own planet, Life on this planet,   and the idea of panspermia that it is something that is worth investigating.

Panspermia – the hypothesis that life exists throughout the University and is distributed by meteoroids, asteroids, comets and contaminated spacecraft.

Here at the University of Kent Impact group we have undertaken a series of projects investigating the survivability of different material during hyper-velocity impacts.

Survivability of Space craft – Space Littering

Most space craft when landing on a planet aims to land safely, known as a soft landing, so that the delicate instruments on board remain intact so that the exploration and science can begin.

Soft landing of the Curiosity rover using the Skye Crane

However, one known mission back in 2005, called NASAs Deep Impact purposefully impacted the comet Tempel-1 to discover the internal composition of the comet. The impactor payload was made of Copper  and Aluminium 4%, weighed 100 kg and impacted the comet at 10.2 km/s. The debris from the impact was analysed to discover more of the internal composition of a comet. However, the projectile was thought to be completely lost during the impact.

Point of Impact of the Deep Impact Mission on to the Temple-1 Comet (NASA/JPL-Caltech/UMD)

However, at the University of Kent we investigated just how much of the Deep Impact projectile would have survived the impact and littered the comet surface with Copper material.

We used Cu ball bearings and impacted them at range of speeds, 1 – 6 km/s, into porous water ice. After the impact the ice is melted and filtered so that any material the survived the impact could be collected.

Our work concluded that up to the impact speed of 10.2 km/s significant material survived the impact, up to 15% of the original mass.

This is a significant result that highlights the effect our own space travel may be having on the Solar System, as Temple -1 now is travelling with some exotic Cu fragments that originate from Earth. This also highlights the importance of the sterilization of space craft material to prevent accidental contamination of the planetary bodies.

Astrobiology – Survivability of biological Material

Astrobiology is the study of life or possible life forming regions in the Solar system beyond Earth. The idea of panspermia means that life would have to survive impact processes to allow them to  begin thriving in the new environment.

We have been interested in this idea, led by our group leader Prof Mark Burchell, for a long while investigating  the survivabillity of simple organic material, bacteria, yeast, tardigrades and even fossilized material.

Fossil Fragments identified after impacts of up to 6 km/s

All these experiments used a frozen projectile which contained the organic material which was then impacted into a ocean target (water). The water is then collected and filtered and the living state of the organisms tests.

It has been found the tardigrades can survive impacts upto 4km/s,
Yeast has a survivbility probability of 10^-3% at 7.4 km/s
Natural Material – Survivability of natural Space material

Of course Natural material form space are known to survive impacts as material that does survive are known as meteorites, however investigating the survivability and the impact speed is a field of interest.

We have done a lot of work on this subject including some exciting ongoing work looking at at the survivability of basalt projectile material which will form a blog post all of its own so Watch this Space!

However if you are eager to learn more please check out the work by Joy et al., 2012 and Asphaug, 2013 who have found evidence of projectile material within the craters on the Moon

Who here has seen Armageddon ? Deep Impact ? The Avengers Age of Ultron ? Gravity?

These films and many others all have a major threat, a asteroid/comet/moon/ ,we shall just say a planetary body / artificial satellite, hitting the Earth or Space craft and the resulting impact causing the destruction of Earth and the end of life as we know it, similar to what happened to the poor dinosaurs.

T-Rex was a Terrible Asteroid Hunter (alexhp RedBubble)

The process of two bodies colliding in space is known as Impact cratering and has been occurring on all planetary bodies since the very early history of the Solar System.

The resulting impact craters from these dynamic events are found on all bodies in the Solar system, including Earth, and shows a detailed volatile history of our own Solar System, and such events are still happening to day with >80 000 meteorites >10 grams impacting the Earth every Year.

Large Impact crater of Saturn’s moon of Mimas – Or the Death Star…. NASA/JPL/SSI

Here at the University of Kent we have a very special piece of equipment to investigate collisions between different materials to simulate impacts that occurred in the Solar system, we have  a REALLY BIG GUN!

The Light Gas Gun at the University of Kent

It is a two stage Light Gas Gun (LGG), which can fire material up to 3 mm sq between 0.5 and 7 km/s, yes that is Kilometer per second!

Why so fast? This is to reach similar speeds to that of material in space

How does the LGG work ?

The LGG works because of the two stage mechanism, the first stage uses rifle powder within a shot gun shell similar to a normal gun. When fired the energy released from the combustion of the powder propels forward a nylon piston rather then a metal bullet.

Schematic of the LGG

The piston travels down the pump tube and compresses the light gas that is present. The compression of this gas builds up the pressure against the rupture disc until it finally fails and the release of pressure from the compressed gas propels the sabot containing the projectile material down a rifled launch tube through the blast tank and light curtains into the target chamber until impacting the target material.

The type of gas, usually H or He,  and the initial pressure are selected to produced the required speed of the impact. The light curtains are used to calculate the speed of the projectile using the simple formula below as we know the distance between the two light curtains and the time the projectile passes thought.

Speed = Distance/Time

So why do we need to fire small things at such high speeds?

The research using the LGG at the University of Kent is diverse with impact cratering being linked to a number of different fields in space and geological sciences. We are currently investigating the possibility of living organisms  surviving impact cratering events. We have also recently investigated the synthesis of amino acids from energy provided by a impact event. Check out the results HERE.

Other work includes geological changes that occur during an impact event including impact melting, loss of water.

The next Blog post will go into more detail of the research undertaken using the LGG.

So, now I hope you know why we use a big gun to investigate impact cratering events that have occurred and are occurring in the Solar System.

Need to know more? Check out these links:

University of Kent

Impact group Twitter

Impact group Youtube