Descrizione del progetto
Campo magnetico della Terra e scomparsa dei Neanderthal
Il campo magnetico della Terra è diminuito di circa il 20 % negli ultimi 150 anni. Poiché la Terra è costantemente sottoposta a radiazioni cosmiche, l’intensità dipende dalla forza del campo magnetico. Nell’arco dei periodi geologici si sono registrati periodi di diminuzione del momento di dipolo magnetico, e quindi del campo magnetico, che possono essere associati a cambiamenti nella polarità del dipolo o a semplici escursioni geomagnetiche. Durante questi periodi, le radiazioni UV sono in grado di penetrare più in profondità nell’atmosfera. Il progetto REVA, finanziato dall’UE, studierà tale «finestra» UV durante le escursioni geomagnetiche di Mono Lake e di Laschamps, che costituiscono eventi importanti se si considera la loro globalità e le possibili implicazioni per l’evoluzione umana (in quanto furono contemporanee alla scomparsa dei Neanderthal).
Obiettivo
"The Earth is constantly subjected to cosmic radiation, the intensity of which, at the level of the upper atmosphere and the Earth's surface, depends on the strength of the magnetic field (MF) surrounding our planet. Over geological timescales, there have been periods of collapse of the magnetic dipole moment, and therefore of the MF, which can be associated with changes in the polarity of the dipole or with simple geomagnetic excursions (GE). GE events (typically lasting ~1ka to ~10ka) generate an increase in cosmic bombardment in the upper atmosphere and, ultimately, through chemical effects the destruction/thinning of the ozone layer. During these periods UV radiation can penetrate deeper into the atmosphere, while it is otherwise absorbed by the ozone layer. Yet, the reality of such a UV ""window” has never been attested by natural observations, which if present during GE events in the future would have significant environmental and above all human consequences. This is plausibly foreseen in a short term as the intensity of Earth’s MF has decreased (~20%) over the past 150 years and with an accelerated rate in the last decades (> ~10 times the normal). The aim of this project is, therefore, to test the reality of a UV window during the Mono Lake-Laschamps (~ -40 ka) GE event, which by its magnitude, its globality and the possible implications for human evolution (being contemporaneous with the disappearance of the Neanderthals), is an example of a remarkable case study. Here, by measuring stable isotopic composition of sulfur (S) at high resolution (<200 years) in ice cores taken in Antarctica, we will leverage peculiar aspects of atmospheric chemistry of the S-33 isotope. In the absence of ozone, the interaction between SO2 and UV radiation, through photochemical processes, generates mass-independent (Δ) signatures. We propose to trace a possible UV ""window"" by analyzing the evolution of the observed ΔS-33 anomaly and model the extent of depletion of ozone layer."
Campo scientifico
Parole chiave
Programma(i)
Argomento(i)
Meccanismo di finanziamento
MSCA-IF - Marie Skłodowska-Curie Individual Fellowships (IF)Coordinatore
75794 Paris
Francia