Vesta, "the asteroid" is a planet covered by calderas and fault zones not just craters and the whole surface has melted and flowed, many times. Vesta is amazing!
By Chris Landau (geologist)
Dear Dawn Team and Marc Rayman
I cannot keep reading the absolute nonsensensical interpretations of what you are seeing on Vesta on your image of the day discussions. You have done such a superb job of getting the dawn spacecraft to Vesta. You have done a grand job in photographing the surface. Now you need a team of field geologists that can interpret what you are seeing. You are letting your interpretive team ruin all your hard work. Vesta will be the most talked about planet in the solar system soon. To put it mildly your planetary interpretive geological team has clearly never done any field mapping. They are very, very bad.
Your team interprets every crater as an impact crater. There are many large non impact features that are clearly not caused by external but by internal volcanism. That is right. The pictures fit the description. Do not worry about the classic radioactive decay interpretation for heating this planet, as not being enough for a body of this size. Radioactive decay has not heated this planet. It has clearly been heated by spin and magneto induction coupling and uncoupling with the spin paired gas giant couplet of Jupiter and Saturn and the spin paired couplet of Earth and Mars.
When an impact occurs, material is scattered in all directions. You do not get micro craters in long linear chains in razor sharp lines, curved or straight for 20 kilometers with each crater perfectly preserved.
When one half of a crater or caldera (let us say the southern half) is perfectly preserved and an area of disturbed rocky area runs between this crater and another crater to the north where only its southern half of this northern crater is melted, then you have to put 2 and 2 together to realize that the disturbing tectonic event lies between the two craters. This is clearly seen the images of the day for March 29, March 30, April, 2 and 3, 2012. There are many other instances in your archives, including at the crater Helena, displayed on April 2 2012.
http://dawn.jpl.nasa.gov/multimedia/imageoftheday/image.asp?date=20120402 April 2 2012 Helena Caldera
The interpretation for the March 29 should be the other way around. The large "crater" and it was not a "crater" but a caldera came later as can clearly be seen by the striations of the larger crater running through the smaller crater. The smaller crater has not superimposed any features on the larger one, yet you claim it came later. Also the smaller crater and there are two, have more degraded rims.
This is either a volcanic dike/dyke, which is a long linear volcanic eruption with gases creating the micro calderas (not caused by external forces but by planetary internal heat.) It could also be a fault or lineament where gases have also bubbled out in a zone of weakness. Think about it. Does it not make more sense?
For the image of the day, placed on the JPL web site on April 4, 2012, the person describing the image keeps talking about "ejecta blankets" of dust when of course there is no such thing as the craters would not be so perfectly preserved in an unconsolidated surface. The whole surface has melted and flowed and many times in the past. The surface is rock solid. Look at all the flow structures of molten rock!
There is so much more to this oblate spheroid that your team is not discussing. You are wasting valuable time. As we all know, Dawn moves on to Ceres in a few months. You can use what you have discovered to help with the interpretation of Ceres. Get a geological team organized that can help map this planet. You can create a global fascination. Use what you have got. The answers lie in front of you if you would only look and not interpret before you look.