Cfrgtkky

I just get this error between my abstract and introduction.

! Undefined control sequence.

u8:´ ->IeC {textasciiacute 

                               }

l.96 keywords

               {asteroid --

? 

and the code:

documentclass{aa} 

    usepackage{array}  

    newcolumntype{C}{>{$}c<{$}}

    usepackage{adjustbox}

    usepackage[skip=0.333baselineskip]{caption}

    usepackage{booktabs, 

                amsmath,  

                siunitx}  

    usepackage{url}

    usepackage{graphicx}

    usepackage{xspace}



    usepackage{txfonts}

    usepackage{hyperref}







    % To add links in your PDF file, use the package "hyperref"

    % with options according to your LaTeX or PDFLaTeX drivers.

    %



        begin{document} 

              abstract

         {Asteroids have been exposed to impacts over eons, and, as a consequence, their surfaces are covered by small particles, pebbles, and boulders. The Japanese JAXA/ISAS Hayabusa mission collected micron-sized particles from the regolith of asteroid 25143 Itokawa. Here we present the results from a study of the mechanical and magnetic properties of three of these particles. The derived results are compared with those obtained from the Chelyabinsk meteorite. The reduced Young´s modulus values obtained for the Itokawa samples are higher than those measured previously for the Chelyabinsk meteorite, indicating that they are more compacted than the minerals forming LL chondrites. The magnetic properties also certify the presence of Ni and Fe in the Itokawa regolith particles.}

        keywords {asteroid -- 

            regolith --

            nanoindentation --

             magnetic

            }



        maketitle



        section{Introduction}



        The JAXA/ISAS Hayabusa spacecraft had a rendez-vous with asteroid 25143 Itokawa and collected regolith samples from its surface after landing on the asteroid in November 2005. The collector sample-return capsule returned to Earth in June 2010 (cite{yano2006touchdown}). The remote study of Itokawa reflectance properties revealed that the asteroid spectrum was consistent with that of an S-type asteroid, and its bulk mineralogy characteristic of the LL group of ordinary chondrites (cite{abe2006near}). The surface of Itokawa consists of large stones and rocks, which are non-uniformly distributed, and a regolith essentially made of pounded stones and small grits (cite{saito2006detailed}). A variety of boulders ranging from meters to hundreds of meters in diameter was also identified by the Hayabusa spacecraft (cite{saito2006detailed}). The re-arrangement of rocks and boulders on the surface of this rubble pile asteroid and the noticed displacement of the regolith were also explained to be consequence of collisions and related processes (cite{saito2006detailed}; cite{matsumoto2016nanomorphology}). 



        end{document}

The input

Young´s

is wrong, as it has U+00B4 ACUTE ACCENT instead of ' or ’ (the former is U+0027 APOSTROPHE, the latter is U+2019 RIGHT SINGLE QUOTATION MARK).

It's much better if you fix the input. If you're in a hurry, add

AtBeginDocument{DeclareUnicodeCharacter{00B4}{'}}

in your preamble.