Impact and habitability scenarios for early Mars revisited:

[beecee]

https://phys.org/news/2022-02-zircon-one-off-gift-mars.html

Shocked zircon find a 'one-off gift' from Mars:

Curtin University researchers studying a Martian meteorite have found the first evidence of high-intensity damage caused by asteroid impact, in findings that have implications for understanding when conditions suitable for life may have existed on early Mars.

 

Published in leading journal Science Advances, the research examined grains of the mineral zircon in Martian meteorite NWA 7034. The meteorite, colloquially known as "Black Beauty", is a rare sample of the surface of Mars. The original 320-gram rock was found in northern Africa and first reported in 2013.

Lead author Morgan Cox, a Ph.D. candidate from Curtin's Space Science and Technology Centre (SSTC) in the School of Earth and Planetary Sciences, described the meteorite as a collection of broken rock fragments and minerals, mostly basalt, that solidified and became a rock over time. A zircon found inside the meteorite preserves evidence of damage that only occurs during large meteorite impacts.

more at link.............

 

the paper:

https://www.science.org/doi/10.1126/sciadv.abl7497

Impact and habitability scenarios for early Mars revisited based on a 4.45-Ga shocked zircon in regolith breccia:

Abstract

After formation of a primordial crust, early impacts influenced when habitable conditions may have occurred on Mars. Martian meteorite Northwest Africa (NWA) 7034 is a regolith breccia that contains remnants of the earliest Martian crust. The paucity of shock deformation in NWA 7034 was previously cited as recording a decline in giant impacts by 4.48 billion years and evidence for habitable Mars by 4.2 billion years ago. We present new evidence of high-pressure shock effects in a 4.45–billion year–old zircon from the matrix of NWA 7034. The zircon contains {112} shock twins formed in the central uplift of a complex impact structure after 4.45 billion years and records impact pressures of 20 to 30 gigapascals. The zircon represents the highest shock level reported in NWA 7034 and paired rocks and provides direct physical evidence of large impacts, some potentially life-affecting, that persisted on Mars after 4.48 billion years.

[mistermack]

The meteorite impact evidence isn't surprising, as how else could a chunk of Mars end up on Earth? 

Even if it's not evidence of the impact that sent it on it's way to Earth, it's probably coming from an early time of heavy meteorite bombardment.