He argues that perhaps these organisms don't need the lengthy genetic material of typical bacteria to exist, and that perhaps they could be an intermediate form of life - between viruses and bacteria. Particles of magnetite found within the carbonate globules are another hotly debated piece of evidence. Gibson says the bulk of the magnetite crystals found inside the meteorite are between 20 and 40 nm long, while some are as small as 5 nm. But Kerridge argues that while these sizes are smaller than the hypothesized 100-nm organisms in the meteorite, the magnetite crystals are still too big to reasonably exist inside such nanobacteria. A major issue being debated is that of possible contamination from the ice in which the meteorite was found, especially in the wake of recent British results.
Controversy also centers around the formation temperature of carbonate globules.
Several groups have published or are publishing studies that contradict each other. If the temperatures at which the carbonate globules formed was higher than that, it is unlikely they could have harbored life. Romanek argues that, at the temperatures proposed by Harvey's team, the carbonates would have homogenized into one mass. Instead, however, distinct layers can be seen surrounding the globules. Also, he adds, at such high temperatures, PAHs inside the globules would disintegrate.