Comet 67P (Rosetta flew behind his one) compared to Los Angeles

We need a viable surveillance and planetary defense program from asteroids/comets much more than landing a man on Mars.

https://en.m.wikipedia.org/wiki/67P/Churyumov–Gerasimenko

67P/Churyumov–Gerasimenko (abbreviated as 67P or 67P/C-G) is a Jupiter-family comet,[8] originally from the Kuiper belt,[9] with a current orbital period of 6.45 years,[1] a rotation period of approximately 12.4 hours[7] and a maximum velocity of 135,000 km/h (38 km/s; 84,000 mph).[10] Churyumov–Gerasimenko is approximately 4.3 by 4.1 km (2.7 by 2.5 mi) at its longest and widest dimensions.[11] It was first observed on photographic plates in 1969 by Soviet astronomers Klim Ivanovych Churyumov and Svetlana Ivanovna Gerasimenko, after whom it is named. It came to perihelion (closest approach to the Sun) on 13 August 2015.[2][12][13][14]

Churyumov–Gerasimenko was the destination of the European Space Agency's Rosetta mission, launched on 2 March 2004.[15][16][17] Rosetta rendezvoused with Churyumov–Gerasimenko on 6 August 2014[18][19] and entered orbit on 10 September 2014.[20] Rosetta's lander, Philae, landed on the comet's surface on 12 November 2014, becoming the first spacecraft to land on a comet nucleus.[21][22][23] On 30 September 2016, the Rosetta spacecraft ended its mission by landing on the comet in its Ma'at region



Dust and cosmic rays on the surface of the comet in 2016, with stars moving in the background: