Their first line of evidence that the space rock was a chunk of what was originally a large planetesimal came from the size of the diamonds themselves.
The diamonds in the meteorite, which crashed in Sudan's Nubian Desert in October 2008, have tiny crystals inside them that would have required great pressure to form, said one of the study's co-authors, Philippe Gillet.
Was found after the explosion, the meteor was mainly composed of coarse-grained rocks (olivine and pyroxene), which could be formed in the mantle of "planet-Bud", and the concentration of carbon in them was unusually high.
"Owing to their stability, mechanical strength and melting temperature, diamonds very often encapsulate and trap minerals and melts present in their formation environment, in the form of inclusions", said the study by Farhang Nabiei et al.
"It is the first time that we found inclusions in extraterrestrial diamonds", Dr Nabiei said.
They discovered chromite, phosphate and iron-nickel sulfide embedded in the diamond, with compositions and morphologies that could only have occurred under greater pressure than 20 gigapascals - almost 200,000 times that of sea level atmospheric pressure.
"This level of internal pressure can only be explained if the planetary parent body was a Mercury- to Mars-sized planetary 'embryo, ' depending on the layer in which the diamonds were formed", the researchers said in a statement from the Federal Polytechnic School of Lausanne in Switzerland.
NASA satellite to launch will seek new exoplanets
We can say how massive they are and how old they are. "So, in essence we can do the equivalent of an ultrasound scan on them". It will collect about 27 gigabytes - or 6,500 song files - per day and send data back every two weeks.
The researchers studied the diamond samples using a combination of advanced transmission electron microscopy techniques.
Since the tiny diamonds found in the Almahata Sitta meteorites have a similar composition to the ones here on Earth, the logical explanation of how they came to be is that they were fashioned in the same - by "the "normal" static pressure inside the parent body", notes the EPFL.
Also, the diamonds would have formed deep within whatever planet it was from, notes the report.
The Almahata Sitta meteorite is the first evidence of this early stage. When the study authors pointed their microscopes on the inclusions in the diamonds, they discovered that each inclusion contained several different minerals, but always in the same relative proportion to those in the other inclusions.
That lost planet was the size of Mercury or perhaps Mars, researchers now say. Many planetary embryos were Mars-sized bodies, such as the one that collided with Earth to give rise to the Moon. According to the scientists, they reported that this type of conditions can only be possible in large planet body not in all planets.